[autotest] grant chromeos-test the right access in setup script

After mounting /usr/local/autotest, we need to grant
chromeos-test (or the current user) access to that folder.

TEST=Run the script and check file permission.
BUG=None

Change-Id: I81ef169966bb1e0da8a9dcc8989adb8b8f4942c1
Reviewed-on: https://chromium-review.googlesource.com/230630
Tested-by: Fang Deng <fdeng@chromium.org>
Reviewed-by: Prashanth B <beeps@chromium.org>
Commit-Queue: Prashanth B <beeps@chromium.org>
1 file changed