Add $REALM to variables supported by the managed permission updater

This will allow converting password policy permissions

Part of the work for: https://fedorahosted.org/freeipa/ticket/4346

Reviewed-By: Martin Kosek <mkosek@redhat.com>

ipaserver/install/plugins/update_managed_permissions.py

@@ -345,6 +345,7 @@ class update_managed_permissions(PostUpdate):
         if 'replaces' in template:
             sub_dict = {
                 'SUFFIX': str(self.api.env.basedn),
+                'REALM': str(self.api.env.realm),
             }
             legacy_acistrs = [ipautil.template_str(r, sub_dict)
                               for r in template['replaces']]