Scrub results in forwarding/lookup (#2331)

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

plugin/forward/lookup.go

@@ -50,6 +50,7 @@ func (f *Forward) Forward(state request.Request) (*dns.Msg, error) {
 			return state.ErrorMessage(dns.RcodeFormatError), nil
 		}
 
+		ret = state.Scrub(ret)
 		return ret, err
 	}
 
@@ -78,7 +79,7 @@ func (f *Forward) Lookup(state request.Request, name string, typ uint16) (*dns.M
 }
 
 // NewLookup returns a Forward that can be used for plugin that need an upstream to resolve external names.
-// Note that the caller must run Close on the forward to stop the health checking goroutines.
+// Note that the caller MUST run Close on the forward to stop the health checking goroutines.
 func NewLookup(addr []string) *Forward {
 	f := New()
 	for i := range addr {