fix: set ON_ERROR_STOP=1 for psql, so calling scripts get an exit status

[erickedji]

Currently, using postgres:connect with a script passed in through stdin, there is no way to know if the script failed or not.

This change aligns the behavior with https://github.com/docker-library/postgres/blob/eaa1c35769621a6bb1e499073a5812ba478c7688/docker-entrypoint.sh#L196 which returns an exit status.

[erickedji]

First unit test failed with text file busy, doesn't seem linked to the PR:

not ok 1 (postgres:hook:pre-delete) removes app from links file when destroying app # in 1683 ms
# (from function `setup' in test file hook_pre_delete.bats, line 5)
#   `dokku apps:create my-app' failed
# -----> Creating my-app...
# 2024/09/24 10:10:00 open /home/dokku/.basher/bash: text file busy1
#  !     2024/09/24 10:10:00 open /home/dokku/.basher/bash: text file busy1
# 
#  !     Postgres service ls does not exist
#  !     Postgres service ls does not exist
# -----> Destroying my-app (including all add-ons)
# -----> Cleaning up...
# -----> Retiring old containers and images

[josegonzalez]

Transient error, merging :)