network intefaces for OpenVSwitch not started after boot

[Premysl Kouril]

Boot order of openvswitch and ifupdown scripts to bring up interface definitions specified for OVS in /etc/network/interfaces are wrong again. The ifupdown scripts try to bring up ovs interfaces before OVS is actually running which results in failure and the interfaces defined in /etc/network/interfaces are not up after machine boot.

The ordering in openvswitch systemd unit files is wrong and for some reasons the unit file openvswitch-nonetwork.service unit was removed from Bionic without appropriate substitute. We have currently fixed it by modifying openvswitch-switch.service ovs-vswitchd.service and ovsdb-server.service units by moving network-pre.target from After to Before clause.

Thanks,
Prema