keystoneauth knows about a bunch of argparse options that users
from a command line will want. We do a good job of processing them
once they've been collected, but an os-client-config user doesn't
have a great way to make sure that they register all of the options,
especially when once considers that you really want to peek at the
args to see which auth plugin has been selected so that the right
arguments can be registered and displayed.
Depends-On: Ifea90b981044009c3642b268dd639a703df1ef05
Change-Id: Ic196f65f89b3ccf92ebec39564f5eaefe8a4ae4b
ed2f34b06a