fedora.spec: Create openvswitch-ovn package.

fedora.spec: Create openvswitch-ovn package.

This patch creates a new subpackage for OVN, openvswitch-ovn.  It also
installs systemd unit files for ovn-controller and ovn-northd.

If you want to run ovn-controller:

    # systemctl start ovn-controller

If you want to run ovn-northd:

    # systemctl start ovn-northd

Both systemd units are currently set to depend on openvswitch.  If
further ovsdb initialization is required for the OVN databases before
ovn-northd can start, that will be handled automatically by ovn-ctl
when you start the ovn-northd service.

This currently assumes that ovn-northd runs on the same host as
ovsdb-server that is hosting the OVN databases.  That seems like a
reasonable assumption in the current architecture and can be evolved
later when needed.

Signed-off-by: Russell Bryant <rbryant@redhat.com>
CC: Flavio Leitner <fbl@redhat.com>
CC: Ben Pfaff <blp@nicira.com>
Signed-off-by: Ben Pfaff <blp@nicira.com>