packaging: setup: use ENGINE_PGPASS in db validations

align with other dbscript utilities.

Change-Id: Ib20a80aff04ac5f977b55ee9a5e71607292ea8ff
Signed-off-by: Alex Lourie <alourie@redhat.com>
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>