Use application_url in API version document
Use application_url in API version document

this handles the possible vhost in Heat API path correctly
(like http://mucloud.com/heat-api) contrary to host_url.

Change-Id: I2f4dbb7d98fbdf5314d5771309919c5b25a72f94
Story: 2002531
Task: 22075

noironetworks/heat,openstack/heat,noironetworks/heat,openstack/heat