Move designate pre/post dsvm hooks to the designate repo

This moves the basic dsvm gate setup from openstack-infra/config
to the stackforge/designate tree - allowing us to more easily
iterate on changes, while also allowing changes to be gated
by the gate-designate-devstack-dsvm job.

Change-Id: I3c3e869350ce3ac2cf4941648e7b500f2cba1cd0
Merge "Move designate pre/post dsvm hooks to the designate repo"