Remove poor optimization to disable wsrep_sync_wait #3723

Fix inappropriate optimization in detecting backend version
and handling of wsrep_sync_wait

lib/MySQL_Variables.cpp

@@ -56,13 +56,18 @@ bool MySQL_Variables::on_connect_to_backend(MySQL_Connection *myconn) {
 	assert(myconn);
 	auto be_version = myconn->mysql->server_version;
 
+/*
+	// completely remove this part, see suggestion in issue #3723
+	// because in MySQL_Session::handler_again___status_SETTING_GENERIC_VARIABLE()
+	// we handle error 1193 (variable is not found), this optimization here seems
+	// unnecessary, especially because the assumption used here is wrong
 	// verify this is not galera cluster
 	// assume galera cluster has two dashes in a version
 	char* first_dash = strstr(be_version, "-");
 	if (!first_dash || !strstr(first_dash+1, "-")) {
 		myconn->var_absent[SQL_WSREP_SYNC_WAIT] = true;
 	}
-
+*/
 	return true;
 }