PG,osd_types: improve check_new_interval debugging

Backport: bobtail
Signed-off-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>
PG::GetMissing: need to check need_up_thru in MLogRec handler

Backport: bobtail
Fixes: #4534
Signed-off-by: Samuel Just <sam.just@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>