[mediaplayer] fix false expected condition in fake audio renderer

This CL fixes the fake audio renderer used for mediaplayer testing.
Previously, it would report success when packets were expected, the
packets that were actually delivered were as expected, but not all
expected packets were delivered.

TEST: this is test code
Change-Id: I4d0c56f2a4c4fa3b16ac8a9e3b59ac87a174296f
diff --git a/bin/mediaplayer/test/fakes/fake_audio_renderer.h b/bin/mediaplayer/test/fakes/fake_audio_renderer.h
index 08f86cb..ff6fed6 100644
--- a/bin/mediaplayer/test/fakes/fake_audio_renderer.h
+++ b/bin/mediaplayer/test/fakes/fake_audio_renderer.h
@@ -41,7 +41,11 @@
   }
 
   // Returns true if everything has gone as expected so far.
-  bool expected() { return expected_; }
+  bool expected() {
+    return expected_ &&
+           (expected_packets_info_.empty() ||
+            expected_packets_info_iter_ == expected_packets_info_.end());
+  }
 
   // AudioRenderer implementation.
   void SetPcmStreamType(fuchsia::media::AudioStreamType format) override;