title: http proxy setting does not present in salt-minion older versions
body: <p>It seems that http proxy setting in salt-minion does not support in salt-minion older version. Do we have any workaround for this.</p>
  
  <p>When I am running salt command from salt-master, environment variables set in salt minion do not work.I have my http proxy setting in environment variables.but when i am running command from salt-master it does not get variables set in env.</p>
  
  <p>Please let me know if any workaround for this. 
  Salt minion version: 0.17.5</p>