Switch the base URL to git.openstack.org

The git repositories on github for openstack are mirrors of the primary
repositories, which are hosted on git.openstack.org, so switch as much
as I can to using the primary, rather than the github mirror.

Change-Id: Idcfda49a691582055256b830c61e098f4a271339
Merge "Switch the base URL to git.openstack.org"
Merge branch 'master' of github.com:openstack-dev/devstack