Changes

We need to update the bootloader, otherwise the system [https://lwn.net/Articles/852586 will stop booting eventually] (but not immediately). I think this is only necessary after <code>zpool upgrade</code>, and <code>zpool upgrade</code> used to warn us about this, but apparently not anymore? (Maybe it's related to the switch to OpenZFS — unclear.)Presumably you can do this after booting into the new system, but before <code>zpool upgrade</code>.