Fix issue with live stream calling endOfStream.

only issue endOfStream in vod mode.
fix invalid index error.
add test for live endOfStream.
In some situation(such as slow downloading),  (original.mediaSequence + mediaIndex) - update.mediaSequence may be < 0,
It will cause exceptions in place such as: videojs.Hls.prototype.fetchKeys = function(playlist, index)

@@ -644,7 +644,7 @@ videojs.Hls.prototype.drainBuffer = function(event) {
 
   // transition the sourcebuffer to the ended state if we've hit the end of
   // the playlist
-  if (mediaIndex + 1 === playlist.segments.length) {
+  if (this.duration() !== Infinity && mediaIndex + 1 === playlist.segments.length) {
     this.mediaSource.endOfStream();
   }
 };

@@ -1944,4 +1944,22 @@ test('treats invalid keys as a key request failure', function() {
   equal(1, bytes[1], 'skipped to the second segment');
 });
 
+test('live stream should not call endOfStream', function(){
+  player.src({
+    src: 'https://example.com/media.m3u8',
+    type: 'application/vnd.apple.mpegurl'
+  });
+  openMediaSource(player);
+  requests[0].respond(200, null,
+                      '#EXTM3U\n' +
+                      '#EXT-X-MEDIA-SEQUENCE:0\n' +
+                      '#EXTINF:1\n' +
+                      '0.ts\n'
+                     );
+  requests[1].response = window.bcSegment;
+  requests[1].respond(200, null, "");
+  equal("open", player.hls.mediaSource.readyState,
+        "media source should be in open state, not ended state for live stream after the last segment in m3u8 downloaded");
+});
+
 })(window, window.videojs);