TWILL-87 : Adding Container Placement Policy control.

Signed-off-by: Terence Yim <chtyim@apache.org>
Merge branch 'master' into site
(TWILL-101) Schedule HDFS delegation token update before it expires.

Signed-off-by: Terence Yim <terence@continuuity.com>
Make timeout for test cases longer to avoid failing too much in Travis when it get scheduled on relatively slow boxes.
Merge branch 'master' into site