MDEV-9696: CREATE SERVER statement does not replicate in Galera Cluster

Enable replication of CREATE/ALTER/DROP SERVER statements
in Galera cluster.

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

+# On node_1
+CREATE SERVER s1
+FOREIGN DATA WRAPPER mysql
+OPTIONS (HOST 'foo');
+# On node_2
+SELECT * FROM mysql.servers;
+Server_name	Host	Db	Username	Password	Port	Socket	Wrapper	Owner
+s1	foo				3306		mysql	
+ALTER SERVER s1
+OPTIONS (HOST 'bar');
+# On node_1
+SELECT * FROM mysql.servers;
+Server_name	Host	Db	Username	Password	Port	Socket	Wrapper	Owner
+s1	bar				3306		mysql	
+DROP SERVER s1;
+# On node_2
+SELECT COUNT(*)=0 FROM mysql.servers;
+COUNT(*)=0
+1
+# End of test

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

+# Test for CREATE/ALTER/DROP SERVER in Galera cluster
+
+--source include/galera_cluster.inc
+
+--connection node_1
+--echo # On node_1
+CREATE SERVER s1
+  FOREIGN DATA WRAPPER mysql
+  OPTIONS (HOST 'foo');
+
+--connection node_2
+--echo # On node_2
+SELECT * FROM mysql.servers;
+ALTER SERVER s1
+  OPTIONS (HOST 'bar');
+
+--connection node_1
+--echo # On node_1
+SELECT * FROM mysql.servers;
+DROP SERVER s1;
+
+--connection node_2
+--echo # On node_2
+SELECT COUNT(*)=0 FROM mysql.servers;
+
+--source include/galera_end.inc
+--echo # End of test
+

sql/sql_parse.cc

@@ -5649,6 +5649,8 @@ mysql_execute_command(THD *thd)
     if (check_global_access(thd, SUPER_ACL))
       break;
 
+    WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
+
     res= create_server(thd, &lex->server_options);
     break;
   }
@@ -5660,6 +5662,8 @@ mysql_execute_command(THD *thd)
     if (check_global_access(thd, SUPER_ACL))
       break;
 
+    WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
+
     if ((error= alter_server(thd, &lex->server_options)))
     {
       DBUG_PRINT("info", ("problem altering server <%s>",
@@ -5678,6 +5682,8 @@ mysql_execute_command(THD *thd)
     if (check_global_access(thd, SUPER_ACL))
       break;
 
+    WSREP_TO_ISOLATION_BEGIN(WSREP_MYSQL_DB, NULL, NULL)
+
     if ((err_code= drop_server(thd, &lex->server_options)))
     {
       if (! lex->if_exists() && err_code == ER_FOREIGN_SERVER_DOESNT_EXIST)