cros_start_vm: Make it work with multiple USB devices.

This script is designed to work with multiple USB devices like e.g.

 --usb_devices=18d1:4ee7,8087:09e

but it doesn't work without this change.

Change-Id: I5ab10bc3941e1f63d87c6fc2405e76869a6a4756
Reviewed-on: https://chromium-review.googlesource.com/308906
Commit-Ready: David Zeuthen <zeuthen@chromium.org>
Tested-by: David Zeuthen <zeuthen@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
1 file changed