Fix use of "break" within "select" in LocalConnection actorLoop

From the golang spec: 'A "break" statement terminates execution of the
innermost "for", "switch", or "select" statement within the same
function.'  But the LocalConnection actorLoop seems to assume it
skips the "select" and terminates the enclosing "for".

As a result, if something did conn.Shutdown(nil), it would not actually
shutdown the connection. It turns out this is never a problem, because
Shutdown is always called with a non-nil error, even though there is code
in a few places to handle the nil case. By cleaning that up, the dubious
"break" is eliminated.

router/connection.go

@@ -196,13 +196,14 @@ func (conn *LocalConnection) SendProtocolMsg(m ProtocolMsg) {
 
 // Async
 func (conn *LocalConnection) Shutdown(err error) {
+	// err should always be a real error, even if only io.EOF
+	if err == nil {
+		panic("nil error")
+	}
+
 	// Run on its own goroutine in case the channel is backed up
 	go func() {
-		if err == nil {
-			conn.sendAction(nil)
-		} else {
-			conn.sendAction(func() error { return err })
-		}
+		conn.sendAction(func() error { return err })
 	}()
 }
 
@@ -379,9 +380,6 @@ func (conn *LocalConnection) actorLoop(actionChan <-chan ConnectionAction) (err
 	for err == nil {
 		select {
 		case action := <-actionChan:
-			if action == nil {
-				break
-			}
 			err = action()
 		case <-conn.heartbeatTCP.C:
 			err = conn.sendSimpleProtocolMsg(ProtocolHeartbeat)
@@ -398,13 +396,10 @@ func (conn *LocalConnection) actorLoop(actionChan <-chan ConnectionAction) (err
 }
 
 func (conn *LocalConnection) shutdown(err error) {
-	switch {
-	case err != nil && conn.remote == nil:
+	if conn.remote == nil {
 		log.Printf("->[%s] connection shutting down due to error during handshake: %v\n", conn.remoteTCPAddr, err)
-	case err != nil:
+	} else {
 		conn.Log("connection shutting down due to error:", err)
-	default:
-		conn.Log("connection shutting down")
 	}
 
 	if conn.TCPConn != nil {