Ensure we can recover from error during db init

Currently if a failure occurs during the shared-db
hook intialisation sequence after db is inited but
before admin creds have been setup, there is no way
to re-run ensure_admin_credentials. This patch
resolves that issue.

Change-Id: Iad80a0eeae6f94dc89ff994f8e5794c60c272e16
Closes-Bug: 1578351