osd: ignore CRUSH_ITEM_NONE in calc_priors_during

These are not true targets and thus not priors.

Fixes: #8610
Signed-off-by: Sage Weil <sage@inktank.com>
osd: ignore CRUSH_ITEM_NONE in compat_msut_dispatch_immediately

Signed-off-by: Sage Weil <sage@inktank.com>