enter frame accumulation even after dropping one

This logically makes more sense, i.e. we keep draining frames from
fwd.ch until we run out.

router/forwarder.go

@@ -269,7 +269,6 @@ func (fwd *Forwarder) run() {
 			}
 			if !fwd.appendFrame(frame) {
 				fwd.logDrop(frame)
-				continue
 			}
 			if !fwd.accumulateAndSendFrames() {
 				return