[autotest] Use a RetryingAFE for lab_inventory.

We get periodic 500 errors from cautotest due to load.  So,
retry the RPC calls.

BUG=chromium:498883
TEST=run an inventory sample locally

Change-Id: If9d7258f3d7a28b13b74b4edfe4142f4f4bcd707
Reviewed-on: https://chromium-review.googlesource.com/299559
Commit-Ready: Richard Barnette <jrbarnette@chromium.org>
Tested-by: Richard Barnette <jrbarnette@chromium.org>
Reviewed-by: Dan Shi <dshi@chromium.org>
1 file changed