ceph: don't leak snap_rwsem in handle_cap_grant

ceph: don't leak snap_rwsem in handle_cap_grant

When handle_cap_grant is called on an IMPORT op, then the snap_rwsem is
held and the function is expected to release it before returning. It
currently fails to do that in all cases which could lead to a deadlock.

Fixes: 6f05b30ea063a2 (ceph: reset i_requested_max_size if file write is not wanted)
URL: https://tracker.ceph.com/issues/55857
Signed-off-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Luís Henriques <lhenriques@suse.de>
Signed-off-by: Xiubo Li <xiubli@redhat.com>