AAudio: log warning when calling stop but the thread is not started.

The AAudioThread can be just created but not started. In that case, it
is not that serious when calling stop but the thread is not started.

Bug: 283891335
Test: make
Change-Id: I88d2c06c7161ad97b3a9eae1fe3cc0b71845fdef
diff --git a/services/oboeservice/AAudioThread.cpp b/services/oboeservice/AAudioThread.cpp
index 549fa59..502d773 100644
--- a/services/oboeservice/AAudioThread.cpp
+++ b/services/oboeservice/AAudioThread.cpp
@@ -75,7 +75,9 @@
 
 aaudio_result_t AAudioThread::stop() {
     if (!mHasThread) {
-        ALOGE("stop() but no thread running");
+        // There can be cases that the thread is just created but not started.
+        // Logging as warning to attract attention but not too serious.
+        ALOGW("stop() but no thread running");
         return AAUDIO_ERROR_INVALID_STATE;
     }