Now that we can support boxed commands, use it to greatly
reduce the number of parameters (and likelihood of getting
out of sync) when adjusting throttle parameters.

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Message-Id: <1468468228-27827-11-git-send-email-eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>