``dhcp6c`` is not restarted when applying settings when multiple WANs are configured for DHCP6
After #6880 it seems that when applying settings on multiple WANs,
dhcp6c is not restarted so the new configuration isn't picked up.
If I manually kill
dhcp6c before applying changes, then it's started properly and the additional WAN picks up its IPv6 address as it should.
Rebooting also works, naturally.