Stop handling SIGTERM when restarting the host.
Stop handling SIGTERM when restarting the host.

It seems to be getting in the way of reboot in a non-deterministic way.

R=vadimsh@chromium.org
BUG=

Review URL: https://codereview.chromium.org/1293173005 .

luci/luci-py,luci/luci-py,luci/luci-py,luci/luci-py