http_proxy/https_proxy env var is ignored, even if proxy_tunnel: false

[artur-a-brylka]

The edgemicro uses proxy settings of env variables "http_proxy, https_proxy and noproxy" only for apigee communication.

But actual service API calls are only directed via the proxy if
edge_config:
proxy: http:/.....
proxy_tunnel: true
is set.

This behaviour is contradictory to the behaviour described in https://docs.apigee.com/api-platform/microgateway/2.5.x/operation-and-configuration-reference-edge-microgateway#settingupedgemicrogatewaybehindacompanyfirewall

The edgemicro should route the traffic to the target endpoint also via the http_proxy/https_proxy if proxy_tunnel: false, but this does not happen. It returns instead {"message":"tunneling socket could not be established, statusCode=403","code":"ECONNRESET"}