Cleanup cached state in TestUtils::runOnRenderThread

Change-Id: I097217c80db5c509d97ef050633946110fccbc80
diff --git a/libs/hwui/tests/common/TestUtils.cpp b/libs/hwui/tests/common/TestUtils.cpp
index 3440d03..9595a85 100644
--- a/libs/hwui/tests/common/TestUtils.cpp
+++ b/libs/hwui/tests/common/TestUtils.cpp
@@ -162,6 +162,7 @@
 
     renderState.onGLContextCreated();
     rtCallback(renderthread::RenderThread::getInstance());
+    renderState.flush(Caches::FlushMode::Full);
     renderState.onGLContextDestroyed();
 
     // Restore the previous signal handler