aaudio: stop calling virtual methods from destructor

Was calling close(), which is abstract and virtual.
This may have been related to some audioserver crashes.
Also cleaned up some strong pointer handling.

Bug: 63390734
Bug: 63353455
Test: run CTS nativemedia/aaudio many times
Change-Id: Ib95aed60a64771b64395c67f0921c67146f9d10f
diff --git a/services/oboeservice/AAudioServiceStreamMMAP.h b/services/oboeservice/AAudioServiceStreamMMAP.h
index 337252d..257bea9 100644
--- a/services/oboeservice/AAudioServiceStreamMMAP.h
+++ b/services/oboeservice/AAudioServiceStreamMMAP.h
@@ -44,8 +44,7 @@
 
 public:
     AAudioServiceStreamMMAP(uid_t serviceUid);
-    virtual ~AAudioServiceStreamMMAP();
-
+    virtual ~AAudioServiceStreamMMAP() = default;
 
     aaudio_result_t open(const aaudio::AAudioStreamRequest &request,
                                  aaudio::AAudioStreamConfiguration &configurationOutput) override;