limit pending requests
Created by: bwidtmann
during our long term playback tests we realized a lot of playback crashes. we realized that it always happens when there are a lot of rejected requests in parallel. therefore we limited the amount of pending requests in PlaybackTimeRule.
Additionally we made retry attempts and interval configurable. If you set the attempts to a very high number, the player now - with limiting pending requests - can resume playback correctly after lost internet connection (fixes Issue: https://github.com/Dash-Industry-Forum/dash.js/issues/599)