OpenGL2: Fix border for cg_viewsize using HDR/FB-MSAA w/postProcess

If using renderFBO (r_hdr 1 or r_ext_framebuffer_multisample > 0) and
r_postProcess 1, the viewport border (cg_viewsize < 100) which is drawn
before the world scene was drawn to the renderFBO but not copied to the
default framebuffer.

Now 2D before the world scene is drawn to the default framebuffer
directly for r_postProcess 1 like 2D drawn after the world scene.

code/renderergl2/tr_local.h

@@ -1472,7 +1472,6 @@ typedef struct {
 
 	FBO_t *last2DFBO;
 	qboolean    colorMask[4];
-	qboolean    framePostProcessed;
 	qboolean    depthFill;
 } backEndState_t;