frontend: don't copy command arguments to output params

Use only object params and params defined in has_output_params as output
params. This removes unnecessary duplication of params defined both in
object plugins and as command arguments.

This requires all command output params to be properly defined in either
the object plugins or the command's has_output_params. Fix the plugins
where this wasn't true.

https://fedorahosted.org/freeipa/ticket/4739

Reviewed-By: David Kupka <dkupka@redhat.com>

ipaserver/plugins/schema.py

@@ -181,8 +181,7 @@ class command(MetaObject):
 
         if len(command.output_params):
             obj['output_params_param'] = tuple(
-                unicode(n) for n in command.output_params
-                if n not in command.params)
+                unicode(n) for n in command.output_params)
 
         return obj