Fix query result leak during binary upgrade

Fix query result leak during binary upgrade

9a974cbcba00 moved the query in binary_upgrade_set_pg_class_oids to the
outer level, but left the PQclear and query buffer destruction in the
is_index conditional.  353708e1fb2d fixed the leak of the query buffer
but left the PGresult leak. This moves clearing the result to the outer
level ensuring that it will be called.

Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/374550C1-F4ED-4D9D-9498-0FD029CCF674@yesql.se
Backpatch-through: v15