libceph: make ceph_con_revoke() a msg operation

ceph_con_revoke() is passed both a message and a ceph connection.
Now that any message associated with a connection holds a pointer
to that connection, there's no need to provide the connection when
revoking a message.

This has the added benefit of precluding the possibility of the
providing the wrong connection pointer.  If the message's connection
pointer is null, it is not being tracked by any connection, so
revoking it is a no-op.  This is supported as a convenience for
upper layers, so they can revoke a message that is not actually
"in flight."

Rename the function ceph_msg_revoke() to reflect that it is really
an operation on a message, not a connection.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
diff --git a/net/ceph/osd_client.c b/net/ceph/osd_client.c
index 24b427b..ad78705 100644
--- a/net/ceph/osd_client.c
+++ b/net/ceph/osd_client.c
@@ -852,7 +852,7 @@
 
 	if (req->r_osd) {
 		/* make sure the original request isn't in flight. */
-		ceph_con_revoke(&req->r_osd->o_con, req->r_request);
+		ceph_msg_revoke(req->r_request);
 
 		list_del_init(&req->r_osd_item);
 		if (list_empty(&req->r_osd->o_requests) &&
@@ -879,7 +879,7 @@
 static void __cancel_request(struct ceph_osd_request *req)
 {
 	if (req->r_sent && req->r_osd) {
-		ceph_con_revoke(&req->r_osd->o_con, req->r_request);
+		ceph_msg_revoke(req->r_request);
 		req->r_sent = 0;
 	}
 }