Fix ConcurrentModificationException in BT handling

    // Same as getConnectedDevices except it filters out the hearing aid devices that are linked

    // together by their hiSyncId.

    public Collection<BluetoothDevice> getUniqueConnectedDevices() {

        ArrayList<BluetoothDevice> result = new ArrayList<>(mHfpDevicesByAddress.values());

        ArrayList<BluetoothDevice> result;

        synchronized (mLock) {

            result = new ArrayList<>(mHfpDevicesByAddress.values());

        }

        Set<Long> seenHiSyncIds = new LinkedHashSet<>();

        // Add the left-most active device to the seen list so that we match up with the list

        // generated in BluetoothRouteManager.