This change adds a conditional to the _fernet_setup to avoid
overwriting credential-keys when keystone-manage credential-setup
is ran and there are already existing credential keys. This will
mitigate issues where encrypted credential blobs in keystone were
becoming un-decryptable when the credential keys were being
overridden or lost upon upgrading.
Change-Id: Iac2b080d5d44bdf07534126419a1d5dd86055d6b
3b14e77d2a