mobmonitor: Ensure tempdir exists.

BUG=chromium:664275
TEST=local test build deployed

Change-Id: Iec6ba52a4034229289acb4260287c6e9222849ea
Reviewed-on: https://chromium-review.googlesource.com/410064
Commit-Ready: Keith Haddow <haddowk@chromium.org>
Tested-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Keith Haddow <haddowk@chromium.org>
Reviewed-by: Michael Tang <ntang@chromium.org>
1 file changed