packaging: Move installation of systemd to .spec

Currently we install the systemd unit files from the Makefile, but as
this is Fedora specific it is better placed in the Fedora .spec.

Change-Id: Icd38fe7b33aff0d1c4d8b65121a218a69b35a41e
Signed-off-by: Juan Hernandez <juan.hernandez@redhat.com>