MDEV-20335: Extra trans_commit_stmt after rollback caused by incorrect fix of MDEV-14401

Fix incorrect else that should have been else if.

sql/sql_parse.cc

@@ -5487,7 +5487,7 @@ mysql_execute_command(THD *thd)
     if (thd->is_error() || (thd->variables.option_bits & OPTION_MASTER_SQL_ERROR))
       trans_rollback_stmt(thd);
 #ifdef WITH_WSREP
-    if (thd->spcont &&
+    else if (thd->spcont &&
              (thd->wsrep_conflict_state == MUST_ABORT ||
               thd->wsrep_conflict_state == ABORTED    ||
               thd->wsrep_conflict_state == CERT_FAILURE))