packaging: setup: ovirt-engine-setup.conf path for developers

ovirt-engine-setup.conf path was previously build from /etc
causing a permission denied error when running in
developer mode.
Now ovirt-engine-setup.conf path is gereated by Makefile
including PREFIX.

Change-Id: If638078fe073f0ded6601354fb7e4c2d0664d40d
Signed-off-by: Sandro Bonazzola <sbonazzo@redhat.com>