softpipe: can't no-op depth test stage when occlusion query is enabled

Fixes http://bugs.freedesktop.org/show_bug.cgi?id=31479

src/gallium/drivers/softpipe/sp_quad_depth_test.c

@@ -860,6 +860,7 @@ choose_depth_test(struct quad_stage *qs,
    /* look for special cases */
    if (!alpha &&
        !depth &&
+       !occlusion &&
        !stencil) {
       qs->run = depth_noop;
    }