ceph: reset cap hold timeout only for requeued inode

__cap_delay_requeue() only requeue inode which does not
have CEPH_I_FLUSH flag, so avoid reset cap hold timeout
for that inode.

Signed-off-by: Chengguang Xu <cgxu519@gmx.com>
Reviewed-by: "Yan, Zheng" <zyan@redhat.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>