plugin/kubernetes: skip deleting pods (#2853)

Don't add pods to our internal cache that are being deleted. This saves
a field in the struct as well.

Add (extra) comments about adding fields to the
object/{Pod,Service,Endpoint} structs.

Signed-off-by: Miek Gieben <miek@miek.nl>

plugin/kubernetes/object/service.go

@@ -7,6 +7,7 @@ import (
 
 // Service is a stripped down api.Service with only the items we need for CoreDNS.
 type Service struct {
+	// Don't add new fields to this struct without talking to the CoreDNS maintainers.
 	Version      string
 	Name         string
 	Namespace    string