The previous patch was wrong for two reasons:
- you can't put shell commands in a Exec, as there's no shell involved
- while you could split the two on two different Exec, it would not
  work anyhow because the unit runs as the esamesync user, and it cannot
  create the /opt/esame directory if the admin did not create it beforehand.

This one was tested to work; the machine boots correctly.

Not tested with labmanager; it is not supposed to be working properly
until you have working copy in /opt/esame, but it would be interesting
to see how it fails.

Otherwise the service will loop and a freshly installed machine
(or a machine with an empty /opt) will not finish the boot.

We should have none, but, in case there are errors reported by the WoL command,
we do not want to stop the systemd service from starting.

Hopefully this will fix the WOL issues, with machines that are sometimes
ignoring the WOL packet.