pgsql: 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

Branch
------
REL_10_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/9170da96defaddf258550b777a86c8092305cf91

Modified Files
--------------
src/bin/pg_upgrade/server.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)