Support PXE booted machine and machines running from the ISO

[Unix4ever]

The problem with the machines running these ways is that Talos is not installed.
And as it's not installed we can't use META to persist the node unique token.

So we should use the old auth schema (only join tokens) for the machines where Talos is not installed.

Rotating join tokens will make the machines without Talos installed unable to join.

[Unix4ever]

In the next release of Talos we might want to try to address that.
There might be a potential solution for saving this data in the bootloader.