Cleanup incoming stream handler

Cleaned up the incoming RTMP handler to close connections on error.
The code aquireing the RTMP channel was also rewritten to be more
idomatic and easier to follow.

handlers.go

@@ -364,36 +364,38 @@ func handlePublish(conn *rtmp.Conn) {
 	if len(urlParts) > 2 {
 		common.LogErrorln("Extra garbage after stream key")
 		l.Unlock()
+		conn.Close()
 		return
 	}
 
 	if len(urlParts) != 2 {
 		common.LogErrorln("Missing stream key")
 		l.Unlock()
+		conn.Close()
 		return
 	}
 
 	if urlParts[1] != settings.GetStreamKey() {
 		common.LogErrorln("Stream key is incorrect.  Denying stream.")
 		l.Unlock()
+		conn.Close()
 		return //If key not match, deny stream
 	}
 
 	streamPath := urlParts[0]
-	ch := channels[streamPath]
-	if ch == nil {
+	ch, exists := channels[streamPath]
+	if exists {
+		common.LogErrorln("Stream already running.  Denying publish.")
+		conn.Close()
+		l.Unlock()
+		return
+	}
+
 	ch = &Channel{}
 	ch.que = pubsub.NewQueue()
 	ch.que.WriteHeader(streams)
 	channels[streamPath] = ch
-	} else {
-		ch = nil
-	}
 	l.Unlock()
-	if ch == nil {
-		common.LogErrorln("Unable to start stream, channel is nil.")
-		return
-	}
 
 	stats.startStream()