Fix bogus logic for checking data dirs' versions within pg_upgrade.
Commit
9be95ef15 failed to cure all of the redundancy here: we were
actually calling get_major_server_version() three times for each
of the old and new data directories. While that's not enormously
expensive, it's still sloppy.
A. Akenteva
Discussion: https://postgr.es/m/
f9266a85d918a3cf3a386b5148aee666@postgrespro.ru