Fixes #576: Delete all relevant CustomFieldValues ehen deleting a CustomFieldChoice
Fixes #576: Delete all relevant CustomFieldValues ehen deleting a CustomFieldChoice

lampwins/netbox,digitalocean/netbox,snazy2000/netbox,Alphalink/netbox,digitalocean/netbox,snazy2000/netbox,snazy2000/netbox,digitalocean/netbox,lampwins/netbox,snazy2000/netbox,lampwins/netbox,Alphalink/netbox,Alphalink/netbox,lampwins/netbox,Alphalink/netbox,digitalocean/netbox