Change Cinder Cert script to run all Volume tests

The Cinder Cert script currently only runs the Tempest
tests tagged with volume.api, should be all Volume tests
to make sure we get things like attach and other commands
fully tested.

Change-Id: Ic15d2ad6d3616bfde4838873d0c79664b009ef1f
Merge "Change Cinder Cert script to run all Volume tests"
Merge branch 'master' of https://github.com/openstack-dev/devstack