Remove the --net as ports are already exposed Fix #1

[renukasgithub]

Removing --net, ports are already exposed. Also using the docker hosted environment on the MAC does not work.

[incebellipipo]

In web post, motivation behind --host is clearly explained.

We also want to use the network stack of the host, so Cobbler will listen on and offer ip addresses on a subnet that the host is connected to. If it would use it's own network stack Cobbler would only be able to issue addresses in the private docker subnet, which would not really make any sense because every container already gets an address from the docker engine.