Fixed minor memory leak in mysql_backend when gw_decode_mysql_server_handshake failed.

server/modules/protocol/mysql_common.c

@@ -287,7 +287,7 @@ int gw_read_backend_handshake(
                                         pthread_self(),
                                         conn->owner_dcb->fd,
                                         pthread_self())));
-                                
+                                while(head = gwbuf_consume(head, GWBUF_LENGTH(head)));
 				return 1;
 			}