docker: fix improperly running httpd in distgit container
We have a recurring problem with httpd, which manifests itself
in the following way:
1. httpd is running, while supervisorctl thinks it failed
2. It is not accessible e.g. via curl and returns "connection refused"
3. Killing httpd and starting it again fixes the issue
We decided to not burn out a large amount of time on this issue
and just try to hackishly workaround it.
Merges: #1088