aaudio: fix some state transitions

Now requestStop() and requestPause() do the appropriate thing
based on state.
Flush is allowed when OPEN, PAUSED or STOPPED because there might
be pre-roll data.

Bug: 69810494
Test: test_various.cpp
Change-Id: Ie1b306b17734a58fa71b1742bb186482893656b7
diff --git a/services/oboeservice/AAudioServiceStreamBase.cpp b/services/oboeservice/AAudioServiceStreamBase.cpp
index 864fc35..e8c9e41 100644
--- a/services/oboeservice/AAudioServiceStreamBase.cpp
+++ b/services/oboeservice/AAudioServiceStreamBase.cpp
@@ -271,11 +271,11 @@
 }
 
 aaudio_result_t AAudioServiceStreamBase::flush() {
-    if (getState() != AAUDIO_STREAM_STATE_PAUSED) {
-        ALOGE("flush() stream not paused, state = %s",
-              AAudio_convertStreamStateToText(mState));
-        return AAUDIO_ERROR_INVALID_STATE;
+    aaudio_result_t result = AAudio_isFlushAllowed(getState());
+    if (result != AAUDIO_OK) {
+        return result;
     }
+
     // Data will get flushed when the client receives the FLUSHED event.
     sendServiceEvent(AAUDIO_SERVICE_EVENT_FLUSHED);
     setState(AAUDIO_STREAM_STATE_FLUSHED);