MDEV-10545: Server crashed in my_copy_fix_mb on querying I_S and P_S tables

Once THDs have been added to the global "threads" list,
they must modify query_string only after acquiring per-
thread LOCK_thd_data mutex.

sql/log_event.cc

@@ -6022,7 +6022,6 @@ int Load_log_event::do_apply_event(NET* net, rpl_group_info *rgi,
   new_db.str= (char *) rpl_filter->get_rewrite_db(db, &new_db.length);
   thd->set_db(new_db.str, new_db.length);
   DBUG_ASSERT(thd->query() == 0);
-  thd->reset_query_inner();                    // Should not be needed
   thd->is_slave_error= 0;
   clear_all_errors(thd, const_cast<Relay_log_info*>(rli));
 

sql/sql_acl.cc

@@ -2797,7 +2797,7 @@ bool change_password(THD *thd, LEX_USER *user)
 
   if (WSREP(thd) && !IF_WSREP(thd->wsrep_applier, 0))
   {
-    thd->set_query_inner(buff, query_length, system_charset_info);
+    thd->set_query(buff, query_length, system_charset_info);
     WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, (char*)"user", NULL);
   }
 
@@ -2858,7 +2858,7 @@ error: // this label is used in WSREP_TO_ISOLATION_BEGIN
   {
     WSREP_TO_ISOLATION_END;
 
-    thd->set_query_inner(query_save);
+    thd->set_query(query_save);
     thd->wsrep_exec_mode  = LOCAL_STATE;
   }
 #endif /* WITH_WSREP */
@@ -2913,7 +2913,7 @@ int acl_set_default_role(THD *thd, const char *host, const char *user,
 
   if (WSREP(thd) && !IF_WSREP(thd->wsrep_applier, 0))
   {
-    thd->set_query_inner(buff, query_length, system_charset_info);
+    thd->set_query(buff, query_length, system_charset_info);
     WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, (char*)"user", NULL);
   }
 
@@ -3009,7 +3009,7 @@ error: // this label is used in WSREP_TO_ISOLATION_END
   {
     WSREP_TO_ISOLATION_END;
 
-    thd->set_query_inner(query_save);
+    thd->set_query(query_save);
     thd->wsrep_exec_mode  = LOCAL_STATE;
   }
 #endif /* WITH_WSREP */

sql/sql_parse.cc

@@ -7298,10 +7298,9 @@ void mysql_parse(THD *thd, char *rawbuf, uint length,
             Note that we don't need LOCK_thread_count to modify query_length.
           */
           if (found_semicolon && (ulong) (found_semicolon - thd->query()))
-            thd->set_query_inner(thd->query(),
-                                 (uint32) (found_semicolon -
-                                           thd->query() - 1),
-                                 thd->charset());
+            thd->set_query(thd->query(),
+                           (uint32) (found_semicolon - thd->query() - 1),
+                           thd->charset());
           /* Actually execute the query */
           if (found_semicolon)
           {