reload systemd services when installing ovs-dpdk
reload systemd services when installing ovs-dpdk

- This change automatically reloads the systemd services
  daemon when systemctl is installed.
- Without this change stacking would fail on systems using
  systemd on a clean install as the ovs-dpdk services was
  not found.

Change-Id: I6c4507cb9fb16f81a07c5b49f2fd2799794e0abf
partial-bug: #1573885

stackforge/networking-ovs-dpdk,openstack/networking-ovs-dpdk,stackforge/networking-ovs-dpdk,stackforge/networking-ovs-dpdk,openstack/networking-ovs-dpdk