zink: spachain is not recreated correctly when using MSAA on some window systems

When using MSAA, if the window is resized, the swapchain images are reallocated but the rendering happens on the old image so uninitialized buffer are displayed. This doesn't always happen, it often happens under X11.

While investigating it I've found that, when the bug occurs, here this loop doesn't find a swapchain image and zink_surface_swapchain_update isnot called.