aaudio: cleanup code that reads timing model

Only use the clock model for the position when
it is running and when the service is not updating
the FIFO counter.

Bug: 120932593
Bug: 122374244
Test: test_return_stop
Test: test_return_stop -i
Change-Id: I6d6a23b35dca5529b6221e1b3b4a4e6672093bf2
diff --git a/media/libaaudio/src/client/IsochronousClockModel.cpp b/media/libaaudio/src/client/IsochronousClockModel.cpp
index 95b52be..747d0e1 100644
--- a/media/libaaudio/src/client/IsochronousClockModel.cpp
+++ b/media/libaaudio/src/client/IsochronousClockModel.cpp
@@ -60,10 +60,14 @@
     mState = STATE_STOPPED;
 }
 
-bool IsochronousClockModel::isStarting() {
+bool IsochronousClockModel::isStarting() const {
     return mState == STATE_STARTING;
 }
 
+bool IsochronousClockModel::isRunning() const {
+    return mState == STATE_RUNNING;
+}
+
 void IsochronousClockModel::processTimestamp(int64_t framePosition, int64_t nanoTime) {
 //    ALOGD("processTimestamp() - framePosition = %lld at nanoTime %llu",
 //         (long long)framePosition,