MDEV#6266: Changing password fails on galera cluster

Added a check to skip ER_PASSWORD_ANONYMOUS_USER in
case the SET PASSWORD was executed by wsrep applier
thread.

mysql-test/suite/galera/r/grant.result

+#
+# MDEV#6266: Changing password fails on galera cluster
+#
+
+# On node_1
+GRANT SELECT ON *.* TO 'user_6266'@'localhost' IDENTIFIED BY 'pass';
+
+# Now, try changing password for 'user_6266'. This command should also
+# execute successfully on the other node.
+SET PASSWORD FOR 'user_6266'@'localhost' = PASSWORD('newpass');
+
+# On node_2
+SELECT user FROM mysql.user WHERE user='user_6266';
+user
+user_6266
+DROP USER 'user_6266'@'localhost';
+# End of test

mysql-test/suite/galera/t/grant.test

+--source include/galera_cluster.inc
+--source include/have_innodb.inc
+
+--echo #
+--echo # MDEV#6266: Changing password fails on galera cluster
+--echo #
+
+--echo
+--echo # On node_1
+--connection node_1
+GRANT SELECT ON *.* TO 'user_6266'@'localhost' IDENTIFIED BY 'pass';
+--echo
+--echo # Now, try changing password for 'user_6266'. This command should also
+--echo # execute successfully on the other node.
+SET PASSWORD FOR 'user_6266'@'localhost' = PASSWORD('newpass');
+
+--echo
+--echo # On node_2
+--connection node_2
+SELECT user FROM mysql.user WHERE user='user_6266';
+# cleanup
+DROP USER 'user_6266'@'localhost';
+
+--source include/galera_end.inc
+--echo # End of test

sql/sql_acl.cc

@@ -2512,7 +2512,13 @@ int check_change_password(THD *thd, const char *host, const char *user,
     my_error(ER_OPTION_PREVENTS_STATEMENT, MYF(0), "--skip-grant-tables");
     return(1);
   }
-  if (!thd->slave_thread && !thd->security_ctx->priv_user[0])
+
+#ifdef WITH_WSREP
+  if ((!WSREP(thd) || !thd->wsrep_applier) &&
+      !thd->slave_thread && !thd->security_ctx->user[0])
+#else
+  if (!thd->slave_thread && !thd->security_ctx->user[0])
+#endif /* WITH_WSREP */
   {
     my_message(ER_PASSWORD_ANONYMOUS_USER, ER(ER_PASSWORD_ANONYMOUS_USER),
                MYF(0));
@@ -2523,6 +2529,7 @@ int check_change_password(THD *thd, const char *host, const char *user,
     my_error(ER_PASSWORD_NO_MATCH, MYF(0));
     return 1;
   }
+
   if (!thd->slave_thread &&
 #ifdef WITH_WSREP
       (!WSREP(thd) || !thd->wsrep_applier) &&