packaging: setup: Use ovirt engine configfile

Use configfile from ovirt-engine-lib and (a copy of) escape from
ovirt-engine-setup to parse db credential files.

Change-Id: Icdea6a02f2737387a4b89b7156eb2c9ebd248fdd
Bug-Url: https://bugzilla.redhat.com/1070344
Signed-off-by: Yedidyah Bar David <didi@redhat.com>