fix: OpenLDAP docker image reference

[iainh]

Summary

• switch the OpenLDAP module to bitnamilegacy/openldap
• bump the image tag to 2.6.10 (the latest)

[DDtKey]

Seems relevant tests are failing:

   ---- openldap::tests::ldap_users_simple_bind stdout ----
  
  thread 'openldap::tests::ldap_users_simple_bind' panicked at src/openldap/mod.rs:550:9:
  assertion `left == right` failed
    left: 1
   right: 2
  note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
  
  ---- openldap::tests::ldap_access_logs_noauth stdout ----
  
  thread 'openldap::tests::ldap_access_logs_noauth' panicked at src/openldap/mod.rs:577:9:
  assertion `left == right` failed: cn=readers should be read
    left: 2
   right: 3
  
  ---- openldap::tests::ldap_secure stdout ----
  
  thread 'openldap::tests::ldap_secure' panicked at src/openldap/mod.rs:744:9:
  assertion `left == right` failed
    left: 1
   right: 2

(there are some flaky tests as well, you can ignore them if not related to openldap)

[iainh]

The container images in 'bitnamilegacy' should be identical to the 'bitnami' ones so I don't think the test failure were related to my changes, But they were unobtrusive enough to make that I included them.