This change is going to be done in conjunction with Pegleg's shipyard
helper code  such that an auth token can be set as an environment
variable. If present it will be used rather than authenticating
against Keystone. This is a requested change by Darren Dejaeger so
that when using automation such as Jenkins pipelines the user is not
forced to provide their credentials to have shipyard automatically
obtain the token - instead they can obtain their token separately and
provide that token for shipyard to use.