Add update_over_cellular crosh command.

This patch adds a new update_over_cellular crosh command to enable,
disable and get the status of the update over cellular network user
preference.

BUG=chromium:213401
TEST=Ran the command in crosh with "enabled", "disabled" and no arguments.

Change-Id: Ie71a9538a94508a7cafff7b26bf3edd5e808066a
Reviewed-on: https://gerrit.chromium.org/gerrit/60721
Tested-by: Alex Deymo <deymo@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Reviewed-by: mukesh agrawal <quiche@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
1 file changed