GAP: Update Scan Mode state from NVM

During BT ON/OFF set Scan Mode state based on NVM Scan Mode state,
which have stored scan mode state. Otherwise, default Scan Mode
state is always set to SCAN_MODE_NONE and application will not
take the state from NVM.

When USER switch happen Scan Mode is set to NONE to avoid improper
scan mode state.

Change-Id: I87117e94cdd898991c720ad6ac72bfa3bb0366f5
CRs-Fixed: 519661, 691014
Conflicts:
src/com/android/bluetooth/btservice/AdapterProperties.java