Changed MixedBulkWriteOperation to take a List<? extends WriteRequest>
Changed insert/insertMany methods in new CRUD API to return void
In AsyncQueryBatchCursor, setting connectionSource to null after release so that it's not double-released if killCursor is called more than once.

 JAVA-1566
Removed unused imports
NettyStream does need some synchronization between threads calling readAsync and Netty threads calling methods in InboundBufferHandler class

 JAVA-1587
Give a bit more time to selectServer in our tests.  1 second is not enough for Jenkins