Monitor: Support hwmon service offline during startup

It is possible for fan-monitor to startup before the Hwmonitor service,
causing unhandled exceptions that block system initialization. This fix
catches the exception until a proper hwmon presence detector is
deployed.

If the exception is caught, this code change forces a re-subscription
during the poweron event to ensure tach sensors will receive published
updates upon resumption of the hwmon service.

Signed-off-by: Mike Capps <mikepcapps@gmail.com>
Change-Id: I8e696e747c432d7a6f696c5ccd9dab73abf7708f
2 files changed