Add endpoint handling to Token/Endpoint auth

This auth plugin was initially created before get_endpoint was
available. Implement the get_endpoint method so that we can use the
plugin with relative URLs.

Closes-Bug: #1323926
Change-Id: Ic868f509e708ad29faf86ec5ceeab2a9c98a24fc
Fix tests to use UUID strings rather than ints for IDs

Several tests were using ints rather than strings for IDs. The ints
were changed to UUID strings.

Change-Id: I65312509c72078c08ca284e313104e926d9885ba
Remove _factory methods from auth plugins

This was a simple factory that would give compatibility for the existing
client to load up the appropriate auth plugin. A more robust plugin
loading mechanism is coming for this and having it available encourages
other auth plugins that they should be using that where they shouldn't.

Just remove it from the auth plugin class. It shouldn't be used by
anyone else so lets keep it on the client objects.

Blueprint: plugin-params
Change-Id: I0618b646f302300d41c7dd7153a1c0bdc237a745
Merge "Add endpoint handling to Token/Endpoint auth"
Merge "Fix tests to use UUID strings rather than ints for IDs"
Merge "Remove _factory methods from auth plugins"