Band-aid to prevent help subcommand from erroring

The code running in the help subcommand relies on Command plugins being
returned from the manager with their options hash. Stubbing in a blank
hash prevents the command from crashing

What we really need is for CommandOptions to be modeled and passed
through from Go to Ruby so :primary subcommands can be displayed, but
that can be a follow-on task from this quick fix.

lib/vagrant/plugin/remote/manager.rb

@@ -181,7 +181,8 @@ module Vagrant
               sf_class.plugin_name = plg[:name]
               sf_class.type = plg[:type]
               result.register(plg[:name].to_sym) do
-                [proc{sf_class}]
+                # TODO(phinze): wire through CommandOptions and return them here
+                [proc{sf_class}, {}]
               end
             end
           end