Install OVS from source when it was configured like that

Function _neutron_ovs_base_install_agent_packages always tried to
install openvswitch from packages and start it using systemd units.
That was failing when ovs was expected to be installed from source.
This patch fixes that.

Change-Id: Iae8625dd800d30061ea3dbed9eb0dfbe16f21572
3 files changed