packaging: setup: configure pghba for use as postgres

The new implementaion brings setting postgres server
to temporarily accept local socket connections from
postgres user. It is required so that all the work
with local postgres server is done with 'su'-ing to
postgres in all flows.

Change-Id: I7244d9ec7a6b2dc4dbc2c3965b1f26e4b51b66ca
Signed-off-by: Alex Lourie <alourie@redhat.com>