The charm looked for `keystone_juju_ca_cert` on disk
instead of
`/usr/local/share/ca-certificates/keystone_juju_ca_cert.crt`
Synced charm-helpers for
https://github.com/juju/charm-helpers/pull/570
Change-Id: Ib7cfdadc3a75fca951792ef2c2e2b454b1ad021d
Closes-Bug: #1915504