trivial: uefi-recovery: only run the plugin if efivar is available
trivial: uefi-recovery: only run the plugin if efivar is available

This will cause it to disable on systems that are definitely not
relevant.

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