Avoid cancelling the data disconnected notification unnecessarily

The RIL is sending us multiple DATA_STATE_CHANGED broadcasts with the
same information. Cache the state of dataDisconnectedDueToRoaming to avoid
cancelling/sending out multiple notifications unncessarily.

Bug: 18218683
Change-Id: Icc6046f6c18333c86cfacb22e8a0c6f24ed2dac1
1 file changed