This is to fix the condition in secrets_manager used to determine
whether the substitution is secret. It currently checks whether the
potential secret reference contains the substring
of 'key-manager/v1/secrets' but the environment-agnostic way
of doing this is to check whether the secret reference contains
the barbican endpoint registered under CONF.barbican.api_endpoint.
Change-Id: I633021571255c8393e19ec60a614ede981a86d9f