packaging: Added generic DB validations before the upgrade

* This patch adds a simple validatedb.sh script that will run
required validation scripts.

* When a new validation script is added, it should be
added to the validatedb runner script as well.

* During the upgrade, this script is executed and handles
the validations control to corresponding scripts.

* If user decides not to clear DB issues or there's any
other error, the exception is raised.

* Patch also introduces some code cleanups

Change-Id: Ief0e65231bb42b569734cdd2fa6491b645491f98
Bug-Url: https://bugzilla.redhat.com/893459
Signed-off-by: Alex Lourie <alourie@redhat.com>