event: use a separate event timer for each port

event: use a separate event timer for each port

Each port will have its own live with its own timer. If a port just
appeared, it will have its own 30 seconds timer. We also notice
changes independently on each port, so the timer is reset on each
change on a given port.

Also, as a safeguard, update port-related information every 10
minutes. We can catch changes in addresses this way (otherwise,
detecting them via netlink is noisy).