QuickSettings: fix GPS graphic state logic

Current logic shows the gps_off icon once the requesting
app has terminated (inUse = false). expected graphic is
gps_on. To reproduce:
1. Start with the GPS off. Tile has gps_off graphic and
   off text.
2. Tap the tile, graphic turns to gps_on, text turns to on
   (this is the idle state where GPS is on and available,
   but does not acquire satellites).
3. Start Google-Maps, once GPS is locked, graphic changes
   to gps_locked.
4. Now stop Google-Maps. Graphic will change to gps_off
   though you would expect it to return to state (2) above.

PS2: always set iconId=0 unless we have a GPS fix

Change-Id: Id044635016a848bb6bc02032b87e977ba0782f06