MDEV-26499 Fix error "mysql_shutdown failed" during MTR tests

- Fix to avoid mysqltest client getting killed abruptly during
  mysql_shutdown(). When Galera replication is shutdown, wait for
  THDs with `thd->stmt_da()->is_eof()` to disconnect (these are about
  to disconnect anyway).
- Extract duplicate code from `wsrep_stop_replication()` and
  `wsrep_shutdown_replication()` in a new function.
- No need to use a custom `shutdown_mysqld.inc` in galera
  suite. Delete it, so that the one in `mysql-test/include/` is used.
Signed-off-by: Julius Goryavsky <julius.goryavsky@mariadb.com>

mysql-test/suite/galera/include/shutdown_mysqld.inc

-# This is the first half of include/restart_mysqld.inc.
-if ($rpl_inited)
-{
-  if (!$allow_rpl_inited)
-  {
-    --die ERROR IN TEST: When using the replication test framework (master-slave.inc, rpl_init.inc etc), use rpl_restart_server.inc instead of restart_mysqld.inc. If you know what you are doing and you really have to use restart_mysqld.inc, set allow_rpl_inited=1 before you source restart_mysqld.inc
-  }
-}
-
-# Write file to make mysql-test-run.pl expect the "crash", but don't start it
---let $_expect_file_name= `select regexp_replace(@@tmpdir, '^.*/','')`
---let $_expect_file_name= $MYSQLTEST_VARDIR/tmp/$_expect_file_name.expect
---exec echo "wait" > $_expect_file_name
-
-# Send shutdown to the connected server
---shutdown_server
---source include/wait_until_disconnected.inc
-

mysql-test/suite/galera/r/MDEV-26499.result

+connection node_2;
+connection node_1;
+connection node_1;
+connection node_2;
+connection node_2;
+SET GLOBAL debug_dbug="+d,simulate_slow_client_at_shutdown";

mysql-test/suite/galera/t/MDEV-26499.test

+#
+# MDEV-26499
+#
+# This test reproduces some failure on mysql_shutdown() call
+# which manifests sporadically in some galera MTR tests during
+# restart of a node.
+#
+
+--source include/galera_cluster.inc
+--source include/have_debug_sync.inc
+
+--let $node_1=node_1
+--let $node_2=node_2
+--source include/auto_increment_offset_save.inc
+
+--connection node_2
+SET GLOBAL debug_dbug="+d,simulate_slow_client_at_shutdown";
+--source include/restart_mysqld.inc
+
+--source include/auto_increment_offset_restore.inc

sql/sql_parse.cc

@@ -2208,6 +2208,7 @@ bool dispatch_command(enum enum_server_command command, THD *thd,
     my_eof(thd);
     kill_mysql(thd);
     error=TRUE;
+    DBUG_EXECUTE_IF("simulate_slow_client_at_shutdown", my_sleep(2000000););
     break;
   }
 #endif

sql/wsrep_mysqld.cc

@@ -1014,10 +1014,8 @@ void wsrep_recover()
   WSREP_INFO("Recovered position: %s", oss.str().c_str());
 }
 
-
-void wsrep_stop_replication(THD *thd)
+static void wsrep_stop_replication_common(THD *thd)
 {
-  WSREP_INFO("Stop replication by %llu", (thd) ? thd->thread_id : 0);
   if (Wsrep_server_state::instance().state() !=
       Wsrep_server_state::s_disconnected)
   {
@@ -1030,40 +1028,30 @@ void wsrep_stop_replication(THD *thd)
     }
   }
 
-  /* my connection, should not terminate with wsrep_close_client_connection(),
-     make transaction to rollback
-  */
-  if (thd && !thd->wsrep_applier) trans_rollback(thd);
+  /* my connection, should not terminate with
+     wsrep_close_client_connections(), make transaction to rollback */
+  if (thd && !thd->wsrep_applier)
+    trans_rollback(thd);
   wsrep_close_client_connections(TRUE, thd);
- 
+
   /* wait until appliers have stopped */
   wsrep_wait_appliers_close(thd);
 
   node_uuid= WSREP_UUID_UNDEFINED;
 }
 
+void wsrep_stop_replication(THD *thd)
+{
+  WSREP_INFO("Stop replication by %llu", (thd) ? thd->thread_id : 0);
+  wsrep_stop_replication_common(thd);
+}
+
 void wsrep_shutdown_replication()
 {
   WSREP_INFO("Shutdown replication");
-  if (Wsrep_server_state::instance().state() != wsrep::server_state::s_disconnected)
-  {
-    WSREP_DEBUG("Disconnect provider");
-    Wsrep_server_state::instance().disconnect();
-    if (Wsrep_server_state::instance().wait_until_state(
-            Wsrep_server_state::s_disconnected))
-    {
-      WSREP_WARN("Wsrep interrupted while waiting for disconnected state");
-    }
-  }
-
-  wsrep_close_client_connections(TRUE);
-
-  /* wait until appliers have stopped */
-  wsrep_wait_appliers_close(NULL);
-  node_uuid= WSREP_UUID_UNDEFINED;
-
+  wsrep_stop_replication_common(nullptr);
   /* Undocking the thread specific data. */
-  my_pthread_setspecific_ptr(THR_THD, NULL);
+  my_pthread_setspecific_ptr(THR_THD, nullptr);
 }
 
 bool wsrep_start_replication(const char *wsrep_cluster_address)
@@ -2644,14 +2632,19 @@ static my_bool have_client_connections(THD *thd, void*)
 {
   DBUG_PRINT("quit",("Informing thread %lld that it's time to die",
                      (longlong) thd->thread_id));
-  if (is_client_connection(thd) && thd->killed == KILL_CONNECTION)
+  if (is_client_connection(thd))
   {
-    WSREP_DEBUG("Informing thread %lld that it's time to die",
-                thd->thread_id);
-    (void)abort_replicated(thd);
-    return true;
+    if (thd->killed == KILL_CONNECTION)
+    {
+      (void)abort_replicated(thd);
+      return true;
+    }
+    if (thd->get_stmt_da()->is_eof())
+    {
+      return true;
+    }
   }
-  return 0;
+  return false;
 }
 
 static void wsrep_close_thread(THD *thd)
@@ -2691,14 +2684,24 @@ static my_bool kill_all_threads(THD *thd, THD *caller_thd)
   /* We skip slave threads & scheduler on this first loop through. */
   if (is_client_connection(thd) && thd != caller_thd)
   {
+    if (thd->get_stmt_da()->is_eof())
+    {
+      return 0;
+    }
+
     if (is_replaying_connection(thd))
+    {
       thd->set_killed(KILL_CONNECTION);
-    else if (!abort_replicated(thd))
+      return 0;
+    }
+
+    if (!abort_replicated(thd))
     {
       /* replicated transactions must be skipped */
       WSREP_DEBUG("closing connection %lld", (longlong) thd->thread_id);
       /* instead of wsrep_close_thread() we do now  soft kill by THD::awake */
       thd->awake(KILL_CONNECTION);
+      return 0;
     }
   }
   return 0;
@@ -2710,6 +2713,7 @@ static my_bool kill_remaining_threads(THD *thd, THD *caller_thd)
   if (is_client_connection(thd) &&
       !abort_replicated(thd)    &&
       !is_replaying_connection(thd) &&
+      !thd->get_stmt_da()->is_eof() &&
       thd_is_connection_alive(thd) &&
       thd != caller_thd)
   {