packaging: use conf.d notation for setup settings

Currently we store setup generated file at /etc/sysconfig/ovirt-engine,
this makes it difficult to manage as user may edit the file as-well.

The service supports /etc/sysconfig/ovirt-engine.d, so we can leverage
this and store setup generated configurations.

User can override these at files with higher index.

Change-Id: Ib05f8c3b21c2b1146bda5b257e347a91d0521bce
Signed-off-by: Alon Bar-Lev <alonbl@redhat.com>