arb_copy_image-formats: avoid undefined behavior
This test uses piglit_multisample_texture(), which doesn't handle
integer formats correctly without invoking undefined behavior.
So let's skip these problematic tests when doing multisampling. We test
them when doing single-sampling anyway, and fixing
piglit_multisample_texture() seems a bit too involved to be worth the
hassle.
Closes: https://gitlab.freedesktop.org/mesa/piglit/-/issues/97
Reviewed-by: Faith Ekstrand <faith.ekstrand@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/piglit/-/merge_requests/858>