packaging: Updated DB validation flow.

This patch is an addition to http://gerrit.ovirt.org/#/c/14389.

It updates the parameters handling in encodingvalidator
utility. Also, it updates calling the validation utilities
with an admin user (postgres) instead of engine.

Change-Id: I34c87815bd667d80f3691ae4a2533523bfa89f29
Bug-Url: https://bugzilla.redhat.com/920565
Signed-off-by: Alex Lourie <alourie@redhat.com>