Do not iterate action.choices if it is none

Do not iterate action.choices in the method add_arguments
in the class OpenStackHelpFormatter if action.choices is
not iterable because it is none.

Change-Id: Ie7110adb798326e5856fddfb6a7365c663b84998
Closes-Bug: #1372152
Fix auth_token for old oslo.config

When running with a havana-level of oslo.config (<1.3.0),
applications with any config options in their api-paste.ini will
fail to start with an error like

 'StrOpt' object has no attribute 'type'

This is because the config options didn't have a type attribute
until 1.3.0.

During the grenade test, the havana level of oslo.config is used,
while the master level of keystoneclient is used, and also in the
havana tests the services are still using the keystoneclient
auth_token middleware.

Change-Id: I745c3e04f18941a2d41e191d43f61b926522bb9d
Closes-Bug: #1372422
Merge "Do not iterate action.choices if it is none"