Feature Addition for issue #3992

I am very much a noob in Go. I have made few changes in the docker code and tested it. It works fine. So what I did is add a new command reload on client and a rest handler for it in api.go. The server calls reload in runtime.go(when /reload is called from client) which pops containers from resource.container list and updates the conf of the popped container with new conf and pushes it back into the list.