Document LISTEN_ADDRESS variable.
The best practices for Docker is to configure with environment variables. Most of gitlab-runner can be configured this way,
however, listen_address is not one of them. Currently one can set
LISTEN_ADDRESS to specify what address to set, which is not really documented anywhere, this is checked before starting the listen server but not saved in the
- Update documentation increase awareness of
LISTEN_ADDRESSto be used upon registering.