[autotest] Add ionice to gs_offloader.

BUG=chromium:375348
DEPLOY=gs_offloader
TEST=ran gs_offloader, ran iotop, saw gsutil at idle io priority

Change-Id: Ie702bcdea42fa9d85b4fbd7b8314e2d72d9eb96c
Reviewed-on: https://chromium-review.googlesource.com/203173
Reviewed-by: Alex Miller <milleral@chromium.org>
Commit-Queue: Alex Miller <milleral@chromium.org>
Tested-by: Alex Miller <milleral@chromium.org>
Reviewed-by: Prashanth B <beeps@chromium.org>
1 file changed