cros-disks: Don't run as root.

BUG=chromium:726036
TEST=platform_CrosDisks*, security_SandboxedServices
CQ-DEPEND=CL:571951,CL:612412

Change-Id: Ie0dcb7df042f091d4c17cda72ba22b139bc8bcaa
Reviewed-on: https://chromium-review.googlesource.com/563738
Commit-Ready: Jorge Lucangeli Obes <jorgelo@chromium.org>
Tested-by: Jorge Lucangeli Obes <jorgelo@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
3 files changed