[RFC][Feature] Adding LDAP_PORT and LDAPS_PORT to configuration env

[kopax]

I want to deploy many docker-openldap on a Mesos cluster.

We use internally HAproxy for TCP reverse proxy See: here.

At this step, I do not know the forward port elected by marathon, and the HAproxy is using the servicePort.

Because the haproxy port is unique, this feature would add possibility to switch the local port used by docker-openldap for ldap:// and ldap://

The environment variables would be:

• LDAP_PORT : set ldap:// port (default: 389)
• LDAPS_PORT : set ldaps:// port (default: 389)

[ghost]

This might also help with running OpenLDAP as a regular user, without root permissions. (See e.g. #109 for an example where this might be handy.)

[colearendt]

Another use case for this - we have hard restrictions on port numbers being > 1024 in one of my kubernetes-based environments, so not being able to easily customize the port has caused a good bit of pain.