dbcheck: Check Deleted Objects and reduce noise in reports about expired tombstones

dbcheck: Check Deleted Objects and reduce noise in reports about expired tombstones

These reports (about recently deleted objects)
create concern about a perfectly normal part of DB operation.

We must not operate on objects that are expired or we might reanimate them,
but we must fix "Deleted Objects" if it is wrong (mostly it is set as being
deleted in 9999, but in alpha19 we got this wrong).

BUG: https://bugzilla.samba.org/show_bug.cgi?id=14593

Signed-off-by: Andrew Bartlett <abartlet@samba.org>
Reviewed-by: Douglas Bagnall <douglas.bagnall@catalyst.net.nz>
Autobuild-User(master): Andrew Bartlett <abartlet@samba.org>
Autobuild-Date(master): Wed Feb  3 05:29:11 UTC 2021 on sn-devel-184