Fix more test timeouts on Tizen.

Like other browsers, the Tizen TV sometimes stalls when inside an
otherwise playable region.  Our technique of flushing by seeking to
the current time doesn't work.  So instead we seek a small amount
in the future.

Closes #893

Change-Id: I91e56e3b9a22fac21fb1d8f66a30a6237b3b28e5

lib/media/playhead.js

@@ -368,7 +368,8 @@ shaka.media.Playhead.prototype.onPollGapJump_ = function() {
               currentTime < buffered.end(i) - 0.5) {
             shaka.log.debug(
                 'Flushing media pipeline due to stall inside buffered range');
-            this.video_.currentTime = this.video_.currentTime;
+            this.video_.currentTime += 0.1;
+            this.stallPlayheadTime_ = this.video_.currentTime;
             break;
           }
         }