Set BRANCH_OVERRIDE to stable/liberty for akanda/astara
Set BRANCH_OVERRIDE to stable/liberty for akanda/astara

We're running 1 week behind integrated release and need to test
against stable/liberty elsewhere.  This can be reverted once
we cut stable/liberty.

Change-Id: I81afdfc792c9166f35ff4ff5ee6c4547c7c8363c

openstack-infra/project-config,Tesora/tesora-project-config,noorul/os-project-config,noorul/os-project-config,dongwenjuan/project-config,dongwenjuan/project-config,Tesora/tesora-project-config,openstack-infra/project-config