FIX: attempt the postgresql update if a stale socket file exists

[mwaniki-wairungu]

If there is a stale socket file when bumping the database version, the current workflow throws spurious errors because of this line in the install_postgres script:

socat /dev/null UNIX-CONNECT:/shared/postgres_run/.s.PGSQL.5432 || exit 0 && echo postgres already running stop container ; exit 1

With this change:

• If postgres is still running, the current behaviour remains the same.
• If postgres was not shut down cleanly, pg_upgrade returns that error.
• If it's just a stale file, pg_upgrade should continue to run.