zink: invoke descriptor_program_deinit for programs on context destroy
this should make multi-context shutdown more stable
affects: glx@glx-visuals-depth -pixmap glx@glx-visuals-stencil
cc: mesa-stable
this should make multi-context shutdown more stable
affects: glx@glx-visuals-depth -pixmap glx@glx-visuals-stencil
cc: mesa-stable