Revert "Get client/share/ltsp/init-ltsp.d/50-machine-id from ltsp-5.5.1,"

This reverts commit 50b33b7d6547d9a7289fdf03ba3de1e3286b8fbc.

Do not do it like this quite yet... the idea is sensible,
but this code does not work for laptops as it is
(there is no network boot device).