stream-controller: use video.buffered.length attribute instead of vid…

…eo.readyState>= HAVE_CURRENT_DATA

to determine whether video is expected to play

related to https://github.com/dailymotion/hls.js/issues/476

src/controller/stream-controller.js

@@ -1096,7 +1096,7 @@ _checkBuffer() {
           logger.log(`target seek position:${targetSeekPosition}`);
         }
         var bufferInfo = BufferHelper.bufferInfo(media,currentTime,0),
-            expectedPlaying = !(media.paused || media.ended || media.seeking || readyState < 2),
+            expectedPlaying = !(media.paused || media.ended || media.seeking || media.buffered.length === 0),
             jumpThreshold = 0.4, // tolerance needed as some browsers stalls playback before reaching buffered range end
             playheadMoving = currentTime > media.playbackRate*this.lastCurrentTime;