Use xenial for bashate
Use xenial for bashate

bashate executes the bashate test, there should be no OS dependency.
Switch node to Xenial.

Change-Id: Ie3d76217946c82f6a92bb8eba53b7176d1e4753c

openstack-infra/project-config,Tesora/tesora-project-config,Tesora/tesora-project-config,openstack-infra/project-config