pg_upgrade: set vacuum_defer_cleanup_age to zero

pg_upgrade:  set vacuum_defer_cleanup_age to zero

Non-zero vacuum_defer_cleanup_age values cause pg_upgrade freezing of
the system catalogs to be incomplete, or do nothing.  This will cause
the upgrade to fail in confusing ways.

Reported-by: Laurenz Albe

Discussion: https://postgr.es/m/7d6f6c22ba05ce0c526e9e8b7bfa8105e7da45e6.camel@cybertec.at

Backpatch-through: 9.5