libceph: reset connection retry on successfully negotiation

We exponentially back off when we encounter connection errors.  If several
errors accumulate, we will eventually wait ages before even trying to
reconnect.

Fix this by resetting the backoff counter after a successful negotiation/
connection with the remote node.  Fixes ceph issue #2802.
Signed-off-by: NSage Weil <sage@inktank.com>
Reviewed-by: NYehuda Sadeh <yehuda@inktank.com>
Reviewed-by: NAlex Elder <elder@inktank.com>

net/ceph/messenger.c

@@ -1629,6 +1629,8 @@ static int process_connect(struct ceph_connection *con)
 		if (con->in_reply.flags & CEPH_MSG_CONNECT_LOSSY)
 			set_bit(LOSSYTX, &con->flags);
 
+		con->delay = 0;      /* reset backoff memory */
+
 		prepare_read_tag(con);
 		break;