Address NTS TCs AUDIO-026-* failures

[ Merge of http://go/wvgerrit/68627 and http://go/ag/5445191 ]

Fix proposed by amlogic. Release usage session early in the CdmEngine
destructor to avoid SIGBUS.

b/118646062
b/120634084
b/120118845
b/122230194

Test: WV unit/integration tests. GtsMediaTestCases. Netflix, Play movies
      playback tests.

Change-Id: If769f9a6bb28b0322894ec74f9b8c33239cbff96

libwvdrmengine/cdm/core/src/cdm_engine.cpp

@@ -86,6 +86,7 @@ CdmEngine::CdmEngine(FileSystem* file_system, const std::string& spoid)
 }
 
 CdmEngine::~CdmEngine() {
+  usage_session_.reset();
   AutoLock lock(session_map_lock_);
   session_map_.Terminate();
 }