BluetoothManagerService: continue teardown when BLE apps registered

    When the adapter is toggled off; when there are BLE apps registered, a
request is sent to unregister all of the BLE apps.  Upon unregister each app
will call through to this function via a callback.  When this gets called if
the ble app count is 0, we can disable everything.  I am keeping track of the
flag so that we know explicitly where we are coming from.

Bug: 34707848
Test: Compile
Change-Id: I9a8322a6fa918e7b410770894c257ec9f7d8d1f5