engine: Refactor InterfaceDaoDbFacadeImpl

Reduced amount of duplicated code, cleared eclipse
warnings and mostly shortening this class.

There is still way to go: changing this class to inherit
from DefaultGenericDaoDbFacade.

Change-Id: I4a46cf2ea27c163ab5ed4fd7c03be37314d9e354
Signed-off-by: Moti Asayag <masayag@redhat.com>