device: fix emission of dhcpX-change dispatcher event
If the address family is the first to complete, we should skip emitting the "dhcpX-change" event and only emit the "up" event.
Also, the "dhcpX-change" event should be emitted every time the lease is updated, not only the first.
Fixes: 58287cbc ('core: rework IP configuration in NetworkManager using layer 3 configuration')