Ensure swift-proxy containers aren't created when not using swift.

* Adjust the environment so that swift_proxy isn't part of infra
* Fix md5sum for environment file in rpc_user_config

HAProxy will work without swift-proxy containers as the group exists
in the inventory but is empty. The VIP will be created but has no
backends.

Fixes: #392
Fixes: #393
Merge pull request #399 from andymcc/swift_env_fix

Ensure swift-proxy containers aren't created when not using swift.