tests:  Fix cut-and-paste error in QuadWithIndexedVertexFetch test.

Looks like the wrong memory barrier was set.
diff --git a/tests/render_tests.cpp b/tests/render_tests.cpp
index b5c0c98..26388ca 100644
--- a/tests/render_tests.cpp
+++ b/tests/render_tests.cpp
@@ -943,7 +943,7 @@
 
     XglIndexBufferObj indexBuffer(m_device);
     indexBuffer.CreateAndInitBuffer(sizeof(g_idxData)/sizeof(g_idxData[0]), XGL_INDEX_16, g_idxData);
-    meshBuffer.BufferMemoryBarrier();
+    indexBuffer.BufferMemoryBarrier();
 
     XglShaderObj vs(m_device,vertShaderText,XGL_SHADER_STAGE_VERTEX, this);
     XglShaderObj ps(m_device,fragShaderText, XGL_SHADER_STAGE_FRAGMENT, this);