osd/osd_types: consider CRUSH_ITEM_NONE in check_new_interval() min_size check

Fixes: #9718
Backport: firefly
Signed-off-by: Sage Weil <sage@redhat.com>
Merge pull request #2708 from ceph/wip-9718

osd/osd_types: consider CRUSH_ITEM_NONE in check_new_interval() min_size

Reviewed-by: Samuel Just <sam.just@inktank.com>