I originally saw this in /var/log/syslog of all my GCE machines that were built
on-top of ubuntu-1604-xenial-v20160610 and older.
See also this bug-report:
I'm now running machines off the image ubuntu-1604-xenial-v20160907a
where I can't reproduce the problem any more.
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Correct hostname not displayed in syslog after boot
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