When migrating from OpenShift SDN to OVNKubernetes with NMState managing br-ex, the mtu-migration service fails after the first reboot. This is because the dependencies do not account for NMState managing the host network config and the primary interface isn't fully configured when it runs. We should have mtu-migration run after the wait-for-primary-ip service, which is how we determine when host networking is ready when using NMState.

Note that this only affects 4.16 because that is the only release in which an OSDN to OVNK migration can happen and the NMState br-ex feature exists.