Fix leak when app does not exit cleanly.

BUG=6452240

Change-Id: I305300fa4e11a8f11e275067f46bde3d5ad1a6e9

driver/rsdGL.cpp

diff --git a/driver/rsdGL.cpp b/driver/rsdGL.cpp
index a935e6f..80fa137 100644
--- a/driver/rsdGL.cpp
+++ b/driver/rsdGL.cpp
@@ -154,6 +154,7 @@
 void rsdGLShutdown(const Context *rsc) {
     RsdHal *dc = (RsdHal *)rsc->mHal.drv;
 
+    rsdGLSetSurface(rsc, 0, 0, NULL);
     dc->gl.shaderCache->cleanupAll();
     delete dc->gl.shaderCache;
     delete dc->gl.vertexArrayState;