k8s_metadata_decorator operator breaks when using a proxy

[jsirianni]

Describe the bug

When HTTP_PROXY is set, the k8s_metadata_decorator attempts to connect to Kubernetes APIs using the proxy. This is by design: type rest.Config

...
// Proxy is the proxy func to be used for all requests made by this
// transport. If Proxy is nil, http.ProxyFromEnvironment is used. If Proxy
// returns a nil *URL, no proxy is used.
//
// socks5 proxying does not currently support spdy streaming endpoints.
Proxy func(*http.Request) (*url.URL, error)

To Reproduce
Steps to reproduce the behavior:

1. Deploy Stanza with HTTP_PROXY set and use the OpenShift plugin
2. Watch stanza logs for error:

{"level":"info","timestamp":"2020-12-31T17:26:23.902Z","message":"Starting stanza agent"}
{"level":"error","timestamp":"2020-12-31T17:26:34.421Z","message":"Failed to start stanza agent","error":{"description":"test connection list namespaces: Get \"https://172.30.0.1:443/api/v1/namespaces\": context deadline exceeded"}}

The agent fails to connect to the Kubernetes API because the Proxy (external to the cluster) cannot reach the kubernetes API (internal to Kubernetes.

Expected behavior

Kubernetes API interactions should be treated as "internal" traffic, and not pass through the proxy that Stanza is using for outgoing connections.

Proxy support for this operator should be an optional parameter, defaulting to false (no proxy).

Environment:

• RHEL 7
• OpenShift 3.11
• Fresh build 92e9403