Feature Notice Addition - docker-proxy high load due software NAT Docker-Proxy

[djdomi]

Describe the issue you are having

Hi,

I've got a bit into a CPU bottleneck for a while, due I use an older Sophos SG 135 with 16 GB of RAM and the CPU starts always crying for overload.

After Investigation, I found out, that the software docker-proxy is eating up my CPU. After a research, I got a hint to disable the user-land proxy. So my Request would be more a hint-request to add to the Tutorial-Section or Setup Notice.

{
    "userland-proxy": false
}

Followed by /etc/init.d/docker restart and the CPU usage went down.

How are you running the container(s)

2, the LAN cache only

### DNS Configuration
Not Necessary
### Output of container(s)
Not Needed.

This is just a notice for the people who have a similar issue.