Telephony: Implementation of IWLAN

- Allow registration polling in radio off state.
- Disable default APN if current RAT is IWLAN.
- Allow non-default PDP activation in radio off state provided
  current RAT is IWLAN.

Set data registration state in APM for IWLAN RAT
- APM causes data registration state to be POWER_OFF. Set it
  to IN_SERVICE for iwlan case
- In APM, UNSOL_VOICE_NETWORK_STATE_CHANGED resets data RAT and
  registration state to POWER_OFF. Ensure that this is done only
  when current RAT is not IWLAN or when iwlan feature is not
  available.

Change-Id: I419f3df987ef90bb5f31b0e381257a81dcc57c3b