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.

Bug-Url: https://bugzilla.redhat.com/1070339
Related-To: https://bugzilla.redhat.com/1065781
Change-Id: I44ae8c9c7cfe10977b05ee8eb7fe9a4ba00becdf
Signed-off-by: Yedidyah Bar David <didi@redhat.com>