dns, passwd: fix outputs of dns_resolve and passwd commands

Use proper output type for the `value` output of the commands.

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

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

ipalib/output.py

@@ -211,3 +211,9 @@ standard_boolean = (
 )
 
 standard_value = standard_boolean
+
+simple_value = (
+    summary,
+    Output('result', bool, _('True means the operation was successful')),
+    Output('value', unicode, flags=['no_display']),
+)