disable fake-hwclock

[jbrzusto]

The (not-yet-released) RPI3B+ version had it enabled; not sure about others.
Needs:

sudo systemctl disable fake-hwclock

This allows us to use timestamps < 1 Jan 2010 to indicate data recorded before the system clock was set. fake-hwclock might have its uses but has the effect of setting the clock to a wrong but plausible time.

SG project maxim: Wrong timestamps should be so wrong that we can tell.