This adds 2 devstack options:
NOVA_V2_LEGACY={True/False} which is whether we'd like to force the
/v2 endpoint to use the legacy v2.0 code base.
it also provides TEMPEST_COMPUTE_TYPE as an way to pass in which
service catalog entry we'd like to use for compute testing.
We also make v2.1 the default compute endpoint, as that's what we'd
like everyone to be testing and using. The other options will let us
build jobs that nova can run to ensure those APIs don't regress.
Change-Id: Ie6b7e4290d9a1d9789d04099b3b31c9a557bc22b
8349aff5ab