This reverts commit 168ca7f0a474f1207ee01dab0ca2e70f34783e9c.
Removing postgresql support from devstack was unnecessary
since it's not broken and not causing maintenance issues
as far as I know. The commit being reverted said that pg
support was deprecated in Pike but nothing in the docs or
commit message refer to official deprecation of postgres
support in devstack or openstack in general. Not to mention
that there are still postgres-based jobs that will no
longer work *and* the notification to the mailing list about
doing this happened *after* it was already done [1] leaving
stakeholders with no time to reply.
[1] http://lists.openstack.org/pipermail/openstack-discuss/2019-October/010196.html
Change-Id: Ie7036d37d79e6aba462b7c97f917e2e7aed108f9
b14665f0dd