aaudio: check for callback thread outside the lock

Calling AAudioStream_requestStop() from a callback is illegal.
But it should just return and error and not hang.
The hang can occur if AAudioStream_close() is called at the same time
from another thread.

Bug: 184370309
Test: adb shell test_disconnect_race
Change-Id: I5e0752611d4d3d3dd994a10e82a339fa39e65d42
diff --git a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
index fdaa2ab..60eb73a 100644
--- a/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
+++ b/media/libaaudio/src/legacy/AudioStreamLegacy.cpp
@@ -124,7 +124,7 @@
                               __func__, callbackResult);
                     }
                     audioBuffer->size = 0;
-                    systemStopFromCallback();
+                    systemStopInternal();
                     // Disable the callback just in case the system keeps trying to call us.
                     mCallbackEnabled.store(false);
                 }