Apply a naming rule of GET to v2 keystone clients

[GET /resources] methods should be "list_<resource name>s"
or "show_<resource name>", so this patch applies the rule
to v2 keystone clients.
This patch changes some v3 parts also because some tests are
shared between v2 and v3 and the method names should be the same.

Partially implements blueprint consistent-service-method-names

Change-Id: Iea7dcb8839d0dfc300295f3e534d54224f9ec31c
23 files changed