Use OpenStack Incubated branding for docs

Zaqar is not integrated but incubated. The branding of the web pages at
http://docs.openstack.org/developer/zaqar/ should thus be the incubated
branding.

Change-Id: Id3b59532fbfd2d344728ee9be4a228811c1ffb82
Merge "Use OpenStack Incubated branding for docs"