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

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

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>
(cherry picked from commit ab8cb34a4b2f60281a4b18b1f1ad23bc2313d91b)