libceph: osd_client: don't drop reply reference too early

(cherry picked from commit ab8cb34a4b2f60281a4b18b1f1ad23bc2313d91b)

In ceph_osdc_release_request(), a reference to the r_reply message
is dropped.  But just after that, that same message is revoked if it
was in use to receive an incoming reply.  Reorder these so we are
sure we hold a reference until we're actually done with the message.

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 680584fab05efff732b5ae16ad601ba994d7b505)