Add sha256 in ceph fetch keys
Add sha256 in ceph fetch keys

fetch_ceph_keys.py is using insecure sha1 function, this patch adds
sha256 beside sha1 - in order to remove sha1 safely in U release.

Change-Id: I32ba1abd204c9dba4bbe3132b5650b0e391616af
Closes-Bug: #1826327

rahulunair/kolla,stackforge/kolla,openstack/kolla,openstack/kolla,rahulunair/kolla,stackforge/kolla,stackforge/kolla