Summary: Fix all known flaky tests, plus minor maintenance
Reviewed-by: martin, chegar

6815766: LinkedBlockingQueue's iterator can return null if drainTo(c) executes concurrently
Summary: Faster, more correct. Use self-linking trick to avoid gc retention
Reviewed-by: martin, dholmes

6800572: Removing elements from views of NavigableMap implementations does not always work correctly.
Summary: Replace use of new TreeSet with new KeySet
Reviewed-by: martin

Reviewed-by: dl, chegar, alanb
Contributed-by: scottb@google.com

6691185: (coll) TreeMap.navigableKeySet's descendingIterator method starts at first instead of last entry
Reviewed-by: dl, chegar