Set param -name automatically (docker run)

``-name`` ist needed for linking containers, i.e. see http://docs.docker.io/en/latest/use/working_with_links_names/#working-with-links-names

plugins/provisioners/docker/client.rb

@@ -80,7 +80,7 @@ module VagrantPlugins
         args << config[:args] if config[:args]
         @machine.communicate.sudo %[
           rm -f #{config[:cidfile]}
-          docker run #{args} #{config[:image]} #{config[:cmd]}
+          docker run #{args} -name #{config[:name]} #{config[:image]} #{config[:cmd]}
         ]
       end