LocationManagerService: Fix race when removing LocationListener

In LocationManagerService if a LocationListener is removed while it has
a pending broadcast the wake lock held while pending broadcasts are
outstanding do not get cleared properly.

There are 2 cases of this race that are fixed:

1. locationCallbackFinished was changed to check the mReceivers HashMap
directly instead of calling getReceiver.  getReceiver would add the
ILocationListener as a new Receiver if it did not exist which caused
a receiver that was removed when it still had a broadcast pending to
be added back in a bad state when the pending broadcast completed.

2. removeUpdatesLocked was changed to decrement the pending broadcasts
when a Receiver is removed that has pending broadcasts.