packaging: removing .pgpass when cleaning DB

We previously used to remove the contents that we put
into the pgpass file. In fact, when we remove the DB
we no longer need this file. So we back it up and remove.

Change-Id: Iff8df6a57bcdf231cbbb54ea732c1fca4afe3a1d
Signed-off-by: Alex Lourie <alourie@redhat.com>