How to enable Docker containers launched by Jenkins to access certain ports on 127.0.0.1?

### Jenkins and plugins versions report

Jenkins Version: 2.450
docker plugin version: 1.6.2

### What Operating System are you using (both controller, and any agents involved in the problem)?

Jenkins deployed in Docker container on Linux host

### Reproduction steps

Fill in the host option in the container configuration, and NPE will be prompted.
Is there any way to allow Docker to access port 127.0.0.1 without configuring the host?

### Expected Results

Enable Docker to access port 127.0.0.1

### Actual Results

Unable to access port 127.0.0.1

### Anything else?

_No response_

### Are you interested in contributing a fix?

_No response_

Start by reproducing the NPE with Jenkins 2.450 and Docker plugin 1.6.2 on a Linux host, using the container configuration's host option. Trace the container networking behavior around access to 127.0.0.1; done means the configuration no longer throws an NPE and launched containers can access the intended port.

Written by the indexing model from the issue text.