MXS-1865 Update server version only when (re)connecting

Updating it every iteration is needless.

server/modules/monitor/mmmon/mmmon.cc

@@ -259,7 +259,7 @@ monitorDatabase(MXS_MONITOR* mon, MXS_MONITORED_SERVER *database)
     database->mon_prev_status = database->server->status;
     mxs_connect_result_t rval = mon_ping_or_connect_to_db(mon, database);
 
-    if (rval != MONITOR_CONN_OK)
+    if (!mon_connection_is_ok(rval))
     {
         if (mysql_errno(database->con) == ER_ACCESS_DENIED_ERROR)
         {