SurfaceFlinger: add more cleanup to unittests

Cleanup the display vectors from Current and Drawing state
of TestableSurfaceFlinger to make sure we don't have any mock
leaked objects.

Bug: 127332154
Test: adb shell /data/nativetest64/libsurfaceflinger_unittest/libsurfaceflinger_unittest
Change-Id: I58f3339ad6ad7b01da6861e07b759611dbd2f9cc
diff --git a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
index 79b5ca0..13059e8 100644
--- a/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
+++ b/services/surfaceflinger/tests/unittests/TestableSurfaceFlinger.h
@@ -341,6 +341,8 @@
         // still be referenced by something despite our best efforts to destroy
         // it after each test is done.
         mutableDisplays().clear();
+        mutableCurrentState().displays.clear();
+        mutableDrawingState().displays.clear();
         mutableEventQueue().reset();
         mutableInterceptor().reset();
         mutableScheduler().reset();