title: add http_proxy to sidecar istio container
body: <p>I enabled istio injection in my namespace
  I'm having trouble to reach an ip:port adress which I already added in my service entry</p>
  <p>I have to set http_proxy env variable to be able to reach that website.</p>
  <p>Is there a way to inject env variable in the sidecar container?</p>