Support client generate literal ipv6 auth_uri base on auth_host

This patch is for fix bug 1208784. Support keystone client generate
literal ipv6 auth_uri via provided auth_host, when the auth_uri is
None.

Fixes bug 1208784

Change-Id: I226881a35a74ef668d4cd1c6829a64c94ff185d9
Merge "Support client generate literal ipv6 auth_uri base on auth_host"