Track session state only when required

The protocol should not track the session state as the parsing is quite
expensive with the current code. This change is a workaround that enables
the parsing only when required. A proper way to handle this would be to do
all the response processing in one place thus avoiding the duplication of
work.

server/modules/protocol/MySQL/mysql_common.cc

@@ -63,6 +63,7 @@ MySQLProtocol* mysql_protocol_init(DCB* dcb, int fd)
     p->changing_user = false;
     p->num_eof_packets = 0;
     p->large_query = false;
+    p->track_state = false;
     /*< Assign fd with protocol */
     p->fd = fd;
     p->owner_dcb = dcb;