softpipe: Flush draw module before switching framebuffer.

Otherwise geometry might end up in the wrong rendertarget.

src/gallium/drivers/softpipe/sp_state_surface.c

@@ -51,6 +51,8 @@ softpipe_set_framebuffer_state(struct pipe_context *pipe,
    struct softpipe_context *sp = softpipe_context(pipe);
    uint i;
 
+   draw_flush(sp->draw);
+
    for (i = 0; i < PIPE_MAX_COLOR_BUFS; i++) {
       /* check if changing cbuf */
       if (sp->framebuffer.cbufs[i] != fb->cbufs[i]) {