vrend: blend: Fix missed glColorMask call

One bug was found when running dEQP-GLES3.functional.fragment_out.random.*.
If run them one by one, they pass. If run them all together, some cases fails.
The fix is: when independent_blend_enable changes from true to false, we should call
glColorMask, otherwise color masks for some color buffers could stay in
stale states.

Signed-off-by: Lepton Wu <lepton@chromium.org>
Reviewed-by: Gert Wollny <gert.wollny@collabora.com>

src/vrend_renderer.c

@@ -4842,7 +4842,9 @@ static void vrend_hw_emit_blend(struct vrend_context *ctx, struct pipe_blend_sta
       else
          glDisable(GL_BLEND);
 
-      if (state->rt[0].colormask != ctx->sub->hw_blend_state.rt[0].colormask) {
+      if (state->rt[0].colormask != ctx->sub->hw_blend_state.rt[0].colormask ||
+          (ctx->sub->hw_blend_state.independent_blend_enable &&
+           !state->independent_blend_enable)) {
          int i;
          for (i = 0; i < PIPE_MAX_COLOR_BUFS; i++)
             ctx->sub->hw_blend_state.rt[i].colormask = state->rt[i].colormask;