[DOCS] Add alternative URL for cloning repo
[DOCS] Add alternative URL for cloning repo

Added github.com URL as an alternative if issues with main repo.

Change-Id: I26623418ba5aea0cb79f502b02c7788e3bfccc6f
Closes-Bug: #1735942

openstack/openstack-ansible,openstack/openstack-ansible,cfarquhar/openstack-ansible,bunchc/openstack-ansible,bunchc/openstack-ansible,stackforge/os-ansible-deployment,cfarquhar/openstack-ansible,stackforge/os-ansible-deployment