rbd: remove linger unconditionally

(cherry picked from commit 61c74035)

In __unregister_linger_request(), the request is being removed
from the osd client's req_linger list only when the request
has a non-null osd pointer.  It should be done whether or not
the request currently has an osd.

This is most likely a non-issue because I believe the request
will always have an osd when this function is called.
Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/ceph/osd_client.c

@@ -907,8 +907,8 @@ static void __unregister_linger_request(struct ceph_osd_client *osdc,
 					struct ceph_osd_request *req)
 {
 	dout("__unregister_linger_request %p\n", req);
+	list_del_init(&req->r_linger_item);
 	if (req->r_osd) {
-		list_del_init(&req->r_linger_item);
 		list_del_init(&req->r_linger_osd);
 
 		if (list_empty(&req->r_osd->o_requests) &&