WIP: device: don't start connectivity checking on unconfigured devices
If the interface has no carrier, no addresses or no routes there is no point in starting a connectivity check on it because we already know that it will fail. Moreover, doing the check on a device without routes causes the addition of a negative entry in the ARP table for each of the addresses associated with the connectivity check host; this can lead to poor network performances.
Edited by Beniamino Galvani