What is the Wait Type "QDS_Shutdown_Queue" referring to?
It's Query Data Store related and you can safely ignore it.
Query store is a new feature in SQL 2016.
Refer to http://www.sqlskills.com/blogs/bobb/more-xevents-in-sql-server-2014-ctp1-dont-wait-any-longer/
Edit:
Below confirms that I was correct - You can safely ignore/filter out this wait type.
Paul Randal has commented in his Wait statistics, or please tell me where it hurts

Dave Mc: Any thoughts on QDS_SHUTDOWN_QUEUE? It’s currently the top reported wait from one of our SQL 2014 prod instances.
Paul Randal : It’s for the Query Store in 2016 – you can filter it out.