Fixed return rc after:

routeQuery()
(dcb->func).close(dcb);

This will prevent setting again dcb->sate = DCB_STATE_POLLING in return_rc label.

The log entry for 

[gw_read_client_event] ioctl FIONREAD for fd 21 failed. errno 9, Bad file descriptor. dcb->state = 3

now is not present anymore.

server/modules/protocol/mysql_client.c

@@ -687,7 +687,7 @@ int gw_read_client_event(DCB* dcb) {
                         /* close client connection */
                         (dcb->func).close(dcb);
                         rc = 1;
-                        goto return_rc;
+                        return rc;
                 }
                 
                 /* MySQL Command Routing */