added libldap-common to packages in Dockerfile

[georglauterbach]

Description

Fixes an issue concerning a package missing on Debian 11. This issue may justify v10.4.1 - please add your opinions on that.

Fixes #2340

Type of change

• Bug fix (non-breaking change which fixes an issue)

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation (README.md or the documentation under docs/)
• If necessary I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes

[casperklein]

This issue may justify v10.4.1

ack

[polarathene]

Any reason our tests didn't catch that as a failure..?

[casperklein]

There are other packages missing, renamed or version bumped, but I don't have time right now to check them:

diff <(docker run --rm -t mailserver/docker-mailserver:10.3 bash -c 'apt list' | cut -d/ -f1 | sort) \
     <(docker run --rm -t mailserver/docker-mailserver:10.4 bash -c 'apt list' | cut -d/ -f1 | sort)

At a first very quick look, fdisk is missing in 10.4. But that's definitely not essential for a mailserver..