Remove duplicate password/token opts.

Consolidate the 'auth' method option registration
in config.py.

This makes it so we don't have to catch Exceptions when the
default 'auth' options are registered twice and avoids some
log WARNING messages as well.

Fixes LP Bug #1154406.

Change-Id: I301328ec3ec4823dd7fbec1e639e2841516352e5
Merge "Remove duplicate password/token opts."