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>
(cherry picked from commit d611eba9caf45f2d977c627b123462a073f523a4)
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>
(cherry picked from commit 4fe4deafbe1758a6b3570048aca57485bd562440)