When openstack runs in HA mode, admin might choose to assign two
separate client certificates for each openstack host. This is
possible with storage_type=none. This change allows deleting cert
and identity based not only on identity name, but on cert pem.
In addition, allow faster cluster recovery in case of certificate
change.
Change-Id: Ia4eea874cfa2bf4befc724b719e53e936292e11f