Verify the usage of this schema feature and the API behaviour.  This
should be the only case where qmp_dispatch() returns NULL.
Signed-off-by: NMarc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NThomas Huth <thuth@redhat.com>