MDEV#5407, MDEV#5386, MVED#4222

Problem: As, wsrep_provider is dynamic and can accept
a valid provider while server is running. Patch for
#4222 wrongly skips the initialization of binlog plugin
during server start, when wsrep provider is not specified.

In wsrep build, if opt_log_bin is not provided, we still
init binlog with wsrep_emulate_bin_log ON.

Fix: This patch fixes #4222 by adding a check to return
from binlog_savepoint_set without proceeding further if
wsrep_on is OFF/false.

This patch also fixes MDEV#5407 and reverts changes pushed
for MDEV#5386 (no longer valid).

sql/log.cc

@@ -1708,7 +1708,7 @@ int binlog_init(void *p)
 {
   binlog_hton= (handlerton *)p;
 #ifdef WITH_WSREP
-  if (WSREP_ON && WSREP_PROVIDER_EXISTS)
+  if (WSREP_ON)
     binlog_hton->state= SHOW_OPTION_YES;
   else
   {
@@ -2217,6 +2217,14 @@ static int binlog_savepoint_set(handlerton *hton, THD *thd, void *sv)
 {
   DBUG_ENTER("binlog_savepoint_set");
 
+#ifdef WITH_WSREP
+  /*
+    If wsrep_emulate_bin_log is true, (i.e opt_bin_log == false),
+    we should return from here if wsrep_on is off.
+  */
+  if (wsrep_emulate_bin_log && !WSREP(thd)) DBUG_RETURN(0);
+#endif /* WITH_WSREP */
+
   binlog_trans_log_savepos(thd, (my_off_t*) sv);
   /* Write it to the binary log */
 #ifdef WITH_WSREP

sql/sql_base.cc

@@ -62,7 +62,6 @@
 
 #ifdef WITH_WSREP
 #include "wsrep_mysqld.h"
-extern handlerton *binlog_hton;
 #endif // WITH_WSREP
 
 bool
@@ -1575,11 +1574,6 @@ void close_thread_tables(THD *thd)
       handled either before writing a query log event (inside
       binlog_query()) or when preparing a pending event.
      */
-#ifdef WITH_WSREP
-     /* In Galera binlog is not enabled by default in case when
-     wsrep provider is not specified. */
-     if ((WSREP_ON && WSREP_PROVIDER_EXISTS) || binlog_hton->state == SHOW_OPTION_YES)
-#endif
     (void)thd->binlog_flush_pending_rows_event(TRUE);
     mysql_unlock_tables(thd, thd->lock);
     thd->lock=0;