ceph: drop messages on unregistered mds sessions; cleanup

Verify the mds session is currently registered before handling
incoming messages.  Clean up message handlers to pull mds out
of session->s_mds instead of less trustworthy src field.

Clean up con_{get,put} debug output.

Signed-off-by: Sage Weil <sage@newdream.net>
diff --git a/fs/ceph/caps.c b/fs/ceph/caps.c
index b6154ff..bb84616 100644
--- a/fs/ceph/caps.c
+++ b/fs/ceph/caps.c
@@ -2600,7 +2600,7 @@
 	struct inode *inode;
 	struct ceph_cap *cap;
 	struct ceph_mds_caps *h;
-	int mds = le64_to_cpu(msg->hdr.src.name.num);
+	int mds = session->s_mds;
 	int op;
 	u32 seq;
 	struct ceph_vino vino;