NFSv4: Fix the return value for nfs_callback_start_svc

returning PTR_ERR(cb_info->task) just after we have set it to
NULL looks like a typo...

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
Cc: Stanislav Kinsbursky <skinsbursky@parallels.com>
diff --git a/fs/nfs/callback.c b/fs/nfs/callback.c
index 9a521fb..5088b57 100644
--- a/fs/nfs/callback.c
+++ b/fs/nfs/callback.c
@@ -241,7 +241,7 @@
 		svc_exit_thread(cb_info->rqst);
 		cb_info->rqst = NULL;
 		cb_info->task = NULL;
-		return PTR_ERR(cb_info->task);
+		return ret;
 	}
 	dprintk("nfs_callback_up: service started\n");
 	return 0;