audiohal: Fix UAF of HAL devices in Stream objects

Stream objects used to hold a pointer to underlying HAL device
object which they didn't own. Since destruction of server side
objects is asynchronous, it was possible that a Device object
gets destroyed before Stream objects, making all the HAL device
object pointer to become stale.

Fixed by adding a strong reference to Device objects into Stream
objects.

Bug: 36702804
Change-Id: I3da3611afbb91d6fd6410ac5b8af2a2eebfa6dac
Test: ran Loopback app and HAL VTS tests
(cherry picked from commit 96d3573cda6f76bcbfc277e69d94914a565218d8)
diff --git a/audio/2.0/default/Device.h b/audio/2.0/default/Device.h
index 46177fc..7738361 100644
--- a/audio/2.0/default/Device.h
+++ b/audio/2.0/default/Device.h
@@ -98,6 +98,8 @@
 
     // Utility methods for extending interfaces.
     Result analyzeStatus(const char* funcName, int status);
+    void closeInputStream(audio_stream_in_t* stream);
+    void closeOutputStream(audio_stream_out_t* stream);
     audio_hw_device_t* device() const { return mDevice; }
 
   private: