In mysql_backend.c:gw_read_backend_event

the delay queue is now consumed when backend_protocol->state == MYSQL_AUTH_FAILED.

This will avoid sending more times the custom error in the threaded configuration.

server/modules/protocol/mysql_backend.c

@@ -265,6 +265,8 @@ static int gw_read_backend_event(DCB *dcb) {
                                         1,
                                         0,
                                         "Connection to backend lost.");
+				// consume all the delay queue
+				dcb->delayq = gwbuf_consume(dcb->delayq, gwbuf_length(dcb->delayq));
                         }
                         /**
                          * Protect call of closeSession.