Bootstrap script breaks due to non-set environment variables

[IngmarPaetzold]

After building the container locally, I had the same issue as #42 and could solve that with https://github.com/jskacel 's proposal:
https://github.com/rroemhild/docker-test-openldap/blob/master/rootfs/opt/openldap/bootstrap/config/tls.ldif#L3-L5

However, the script broke again:

Load data...
++ find /opt/openldap/bootstrap/data -maxdepth 1 -name '*_*.ldif' -type f
++ sort
Processing file /opt/openldap/bootstrap/data/00_people.ldif...
[...]
/opt/openldap/bootstrap/data/30_groups_crew.ldif'
+ for ldif in ${data}
+ echo 'Processing file /opt/openldap/bootstrap/data/00_people.ldif...'
/var/run/s6/etc/cont-init.d/050-openldap-populate: line 43: LDAP_BASEDN: unbound variable
[cont-init.d] 050-openldap-populate: exited 1.
[cont-init.d] done.
[services.d] starting services
starting slapd
[services.d] done.
65002ed6 @(#) $OpenLDAP: slapd  (May 14 2022 18:35:44) $
        Debian OpenLDAP Maintainers <pkg-openldap-devel@lists.alioth.debian.org>
65002ed6 hdb_db_open: database "dc=planetexpress,dc=com": database already in use.
65002ed6 backend_startup_one (type=hdb, suffix="dc=planetexpress,dc=com"): bi_db_open failed! (-1)
65002ed6 slapd stopped.

It fails because variables LDAP_BASEDN and LDAP_DOMAIN are not set, but script /rootfs/etc/cont-init.d/050-openldap-populate references them.
Reason is the set -eux on top which makes every non-set variable an error.

Therefore the script breaks and does not stop the database, which, as consequence, raises the database already in use error.

I will file a pull request for that.