Custom MTU settings docker network

A custom Docker network is created when TenantOS spins up a Docker container for the IPMI (web) console. However, this process ignores the MTU parameter that can be set in /etc/docker/daemon.json.

The VM where our remote agent runs uses a lower MTU value than 1500, which causes connectivity issues inside the Docker container.

We would like to have an option to set a custom MTU value for the Docker network.