Add yet another place where files leak.
Add yet another place where files leak.

This will be migrated server-side soon but it's not yet.

R=vadimsh@chromium.org
BUG=

Review URL: https://codereview.appspot.com/161980043

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py