Allow passing keystone_host to controller class

The different components defaults to 127.0.0.1 for keystone
for the controller class. This fix allows to override that for
situations where the keystone service is not deployed on the
controller.

Change-Id: I982de99d6b96f09dc086f46f8db6acb830211cd6
Merge "Allow passing keystone_host to controller class" into stable/grizzly