Fixing discontinuity seek

On seeking to a discontinuity point, the buffer would not refill and
the player would stop working. This commit fixes that issue, and
adjusts the test to catch the previous failure.

@@ -611,12 +611,17 @@ videojs.Hls.prototype.drainBuffer = function(event) {
   // until it empties before calling it when a discontinuity is
   // next in the buffer
   if (segment.discontinuity) {
-    if (event.type !== 'waiting') {
-      return;
-    }
+    if (event.type === 'waiting') {
       this.sourceBuffer.abort();
       // tell the SWF where playback is continuing in the stitched timeline
       this.el().vjs_setProperty('currentTime', segmentOffset * 0.001);
+    } else if (event.type === 'timeupdate') {
+      return;
+    } else if (typeof offset !== 'number') {
+      //if the discontinuity is reached under normal conditions, ie not a seek,
+      //the buffer already contains data and does not need to be refilled,
+      return;
+    }
   }
 
   // transmux the segment data from MP2T to FLV

@@ -1186,7 +1186,7 @@ test('waits until the buffer is empty before appending bytes at a discontinuity'
   var aborts = 0, setTime, currentTime, bufferEnd;
 
   player.src({
-    src: 'disc.m3u8',
+    src: 'discontinuity.m3u8',
     type: 'application/vnd.apple.mpegurl'
   });
   openMediaSource(player);
@@ -1233,7 +1233,7 @@ test('clears the segment buffer on seek', function() {
   videojs.Hls.SegmentParser = mockSegmentParser(tags);
 
   player.src({
-    src: 'disc.m3u8',
+    src: 'discontinuity.m3u8',
     type: 'application/vnd.apple.mpegurl'
   });
   openMediaSource(player);
@@ -1261,14 +1261,14 @@ test('clears the segment buffer on seek', function() {
   standardXHRResponse(requests.pop());
 
   // play to 6s to trigger the next segment request
-  currentTime = 6;
+  currentTime = 1;
   bufferEnd = 10;
   player.trigger('timeupdate');
 
   standardXHRResponse(requests.pop());
 
-  // seek back to the beginning
-  player.currentTime(0);
+  // seek to the discontinuity
+  player.currentTime(10);
   tags.push({ pts: 0, bytes: 0 });
   standardXHRResponse(requests.pop());
   strictEqual(aborts, 1, 'aborted once for the seek');