qapi: add condition to variants documentation

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20181213123724.4866-21-marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
4 files changed