Bluetooth: do not dimiss fragment when Activity.finish() is called

* When Activity.finish() is called, it's associtated fragments are all
  dismissed automatically
* Cached used fragments are dimissed in onCreate() before new ones are
  created

Bug: 62230203
Test: Pair with Bluetooth device, Settings unit tests
Change-Id: Ieca88ba0660c5407f0d88d572d06a722c642ac39

src/com/android/settings/bluetooth/BluetoothPairingDialog.java

@@ -108,12 +108,6 @@ public class BluetoothPairingDialog extends Activity {
     @VisibleForTesting
     void dismiss() {
         if (!isFinishing()) {
-            BluetoothPairingDialogFragment bluetoothFragment =
-                (BluetoothPairingDialogFragment) getFragmentManager()
-                    .findFragmentByTag(FRAGMENT_TAG);
-            if (bluetoothFragment != null) {
-                bluetoothFragment.dismiss();
-            }
             finish();
         }
     }