Add default auth_uri setting for auth token.

The latest keystoneclient code now gives a Warning if auth_uri
isn't explicitly specified.

Change-Id: I0feb52f7a9140ea750254f80b6a3e6855b25f1d3
Improve support for RHEL derivatives

CentOS, Scientific, SLC, OracleLinux, Amazon, etc. should be treated
just like RedHat.

Change-Id: I8a3ecdf8d0abdd197346bce649bfb51d1158ff79
Merge "Add default auth_uri setting for auth token."
Merge "Improve support for RHEL derivatives"