trivial: fix shutdown error on fwupdtool activate
trivial: fix shutdown error on fwupdtool activate

EXIT_NOTHING_TO_DO needs to be caught by the shutdown script too.
Fixes: #2463

fwupd/fwupd,fwupd/fwupd,hughsie/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd,fwupd/fwupd,hughsie/fwupd