Enable async mode for acpictz sensor

When user_mode policy is used this sensor generates async events,
so enable aysnc mode on this sensor.
Fix ofstream variable init

On some platform init with "" doesn't work. Just use empty init
during constructor init.
Merge pull request #28 from 01org/development_0

Development 0
Merge pull request #29 from 01org/thermal_daemon_next

Thermal daemon next misc fixes for async mode