layers: LX235, Validate all Pipeline VBOs for CommandBuffers

Validation was throwing errors if a CB had extra VBOs bound, and was not
checking each VBO binding explicitly.

Conflicts:
	layers/draw_state.cpp
	tests/layer_validation_tests.cpp
diff --git a/layers/draw_state.h b/layers/draw_state.h
index d935c15..ef0f9c3 100755
--- a/layers/draw_state.h
+++ b/layers/draw_state.h
@@ -417,6 +417,7 @@
     //  each individual CMD_NODE referencing its own "lastBound" state
     VkPipeline                   lastBoundPipeline;
     uint32_t                     lastVtxBinding;
+    vector<VkBuffer>             boundVtxBuffers;
     vector<VkViewport>           viewports;
     vector<VkRect2D>             scissors;
     float                        lineWidth;