ddclient: T3422: Allow zone property with cloudflare protocol
ddclient: T3422: Allow zone property with cloudflare protocol

Allows Dynamic DNS services with custom names to use the zone field if
the protocol is set to cloudflare

(cherry picked from commit 5ab6c20f8acd4dda1870b9a71fe73129d2f78b24)

vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x,vyos/vyos-1x