ceph: break the check delayed cap loop every 5s

In some cases this may take a long time and will block renewing
the caps to MDS.

[ idryomov: massage comment ]

Link: https://tracker.ceph.com/issues/50223#note-21


Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>