block/nbd-client: simplify check in nbd_co_receive_reply

If we are woken up from while() loop in nbd_read_reply_entry
handles must be equal. If we are woken up from
nbd_recv_coroutines_wake_all s->quit must be true, so we do
not need checking handles equality.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <20170920124507.18841-3-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>

block/nbd-client.c

@@ -189,9 +189,10 @@ static int nbd_co_receive_reply(NBDClientSession *s,
     s->requests[i].receiving = true;
     qemu_coroutine_yield();
     s->requests[i].receiving = false;
-    if (s->reply.handle != request->handle || !s->ioc || s->quit) {
+    if (!s->ioc || s->quit) {
         ret = -EIO;
     } else {
+        assert(s->reply.handle == request->handle);
         ret = -s->reply.error;
         if (qiov && s->reply.error == 0) {
             assert(request->len == iov_size(qiov->iov, qiov->niov));