device: restart DHCP when the MAC changes
If the MAC changes there is the possibility that the DHCP client will not be able to renew the address because it uses the old MAC as CHADDR. Depending on the implementation, the DHCP server might use CHADDR (so, the old address) as the destination MAC for DHCP replies, and those packets will be lost.
To avoid this problem, restart the DHCP client when the MAC changes.