This removes the code that might delete a Tahoe-LAFS nodedir and replaces it
with code that will try to save an unexpected copy of it out of the way
instead.

And test for (kind of) SSH availability

This gives us a good opportunity to mention the privacy policy, too.

The new version of PaymentServer has incompatible changes that require this.

so it won't be running yet when this runs

right???

reordering/reformatting just to make commenting easier

maybe the other systemd timer fires right away too

why make it a plugin, then, you may ask.
or perhaps you may not ask.