nbd/client: fix nbd_send_request to return int

Fix nbd_send_request to return int, as it returns a return value
of nbd_write (which is int), and the only user of nbd_send_request's
return value (nbd_co_send_request) consider it as int too.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20170804151440.320927-5-vsementsov@virtuozzo.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
diff --git a/include/block/nbd.h b/include/block/nbd.h
index f745060..040cdd2 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -163,7 +163,7 @@
                           Error **errp);
 int nbd_init(int fd, QIOChannelSocket *sioc, NBDExportInfo *info,
              Error **errp);
-ssize_t nbd_send_request(QIOChannel *ioc, NBDRequest *request);
+int nbd_send_request(QIOChannel *ioc, NBDRequest *request);
 int nbd_receive_reply(QIOChannel *ioc, NBDReply *reply, Error **errp);
 int nbd_client(int fd);
 int nbd_disconnect(int fd);