Fix race condition in monitor_connect_thread

Add wait loop for GloMTH initialization before accessing variables.
Other monitor threads (MonitorPing, MonitorReadOnly, etc.) already had
this pattern, but monitor_connect_thread was missing it.

This fixes Valgrind errors about uninitialized values in
get_variable_uint16() when strcasecmp reads from memory that hasn't
been fully initialized yet.

lib/MySQL_Monitor.cpp

@@ -1339,6 +1339,11 @@ void * monitor_connect_thread(const std::vector<MySQL_Monitor_State_Data*>& mmsd
 	assert(!mmsds.empty());
 	mysql_close(mysql_init(NULL));
 	MySQL_Monitor_State_Data *mmsd = mmsds.front();
+	// Wait for GloMTH to be initialized
+	while (GloMTH==NULL) {
+		usleep(50000);
+	}
+	usleep(100000);
 	if (!GloMTH) return NULL;	// quick exit during shutdown/restart
 	MySQL_Thread * mysql_thr = new MySQL_Thread();
 	mysql_thr->curtime=monotonic_time();