schema plugin: Fix commands without metaobject arg
Previously, all the commands of schema plugin derived from
BaseMetaSearch require metaobject as their argument
(by implementation), but the spec for some of them only optionally
asks for search criteria arg. This patch fixes this inconsistency.
Fixes: https://pagure.io/freeipa/issue/8954
Signed-off-by: Stanislav Levin <slev@altlinux.org>
Reviewed-By: Florence Blanc-Renaud <flo@redhat.com>