common_lib/test.py - Make tmpdir and resultsdir writable for all.

BUG=chromium:362220
TEST=run video_VDAPerf on an arm chromebook

We may write to those directly as chronos instead of root.

Change-Id: I485a712af57442c7e719477fd4b20b5e92eb23e0
Reviewed-on: https://chromium-review.googlesource.com/195121
Reviewed-by: Yuli Huang <yuli@chromium.org>
Tested-by: Owen Lin <owenlin@chromium.org>
Commit-Queue: Owen Lin <owenlin@chromium.org>
1 file changed