Enable Keystone under Apache by default

Make the default run mode of Keystone HTTPD + mod_wsgi. This will
enable gating on Keystone under mod_wsgi.

Depends On: https://review.openstack.org/#/c/100764/

Change-Id: I4b664a1d6c9bbb1ff999158f3a8c8ab3bd8d891b
Merge "Enable Keystone under Apache by default"