Install overwrites custom rancher-system-agent.env file

[agracey]

It appears that the installer is overwriting the .env file at
https://github.com/rancher/system-agent/blob/main/install.sh#L804

This is causing issues with a few users who are behind a corporate proxy. Is there a way to set a proxy to be used when defining a cluster?

[Oats87]

The expectation is that proxies required by the node are defined by the user shell/service shell, and are set in a global location on the node. If the user has the corresponding HTTP_PROXY etc. environment variables set, they should be set for the system agent.

[Oats87]

It's important to note that Rancher doesn't really support communication-through-proxy in the first place, due to potential performance implications. We don't want to open WATCH requests through a corporate proxy for example.