Add query for critical keystone regression

Keystone introduced a backwards incompatibility in it's /endpoints API
where endpoints no longer have 'region' attributes, so heat isn't able
to filter endpoints.

This manifests as a back trace in heat such as:

    StackBuildErrorException: Stack
    heat-337060294/2528f858-2804-4c3e-bd60-970bc470bf28 is in
    CREATE_FAILED status due to 'Resource CREATE failed:
    EndpointNotFound: publicURL endpoint for volume service in RegionOne
    region not found'

Change-Id: I9856c265f05cb118e3d8d4e66c1b43801b919517
Related-Bug: 1364463