[autotest] Enable snapshot clone for Ganeti instance using aufs.

Ganeti instances does not support overlayfs due to older kernel. However, it
does support snapshot clone with aufs. Enable this will greatly enhance SSP
performance in Ganeti instances.

BUG=chromium:464834
TEST=verified in server7 with cbf run
http://chromeos-autotest.cbf.corp.google.com/afe/#tab_id=view_job&object_id=10335

Change-Id: I76a7691033214347d5a4e892cd0776bde8c53433
Reviewed-on: https://chromium-review.googlesource.com/267106
Reviewed-by: Dan Shi <dshi@chromium.org>
Commit-Queue: Dan Shi <dshi@chromium.org>
Trybot-Ready: Dan Shi <dshi@chromium.org>
Tested-by: Dan Shi <dshi@chromium.org>
1 file changed