discover/device-handler: Disable safe mode warning on reinit

If a user pressed "Rescan Devices" in safe mode the reinit would
complete successfully, but the big warning that safe mode is active
would remain. On reinit clear the safe_mode flag properly.

This has no functional change aside from clearing the UI warning - the
IPMI override remains active until cleared or a successful boot occurs.

Signed-off-by: Samuel Mendoza-Jonas <sam@mendozajonas.com>
(cherry picked from commit b9b5fa357e5921eb752e62f7146339007d9f767f)