Bug 877530 - B2G Emulator: voice/data is always connected even device is in airplane mode

Please see [bug 877530](https://bugzilla.mozilla.org/show_bug.cgi?id=877530).

Some behavior of emulator are different with unagi. I believe we should make emulator acting more like a real device. Below are the behavior of unagi:
* Sim status is reported as ABSENT when radio is off.
* When there is no network service, the RIL_REQUEST_OPERATOR will have a success response with empty result instead of an error. 
* Still process RIL request even if radio is off.