This reverts commit 3113a3e6.

Thinking a second time:  While the staging grid is deployed to
by an automaton anyway and it taking a minute longer won't bother
us, 20 % space savings is probably not worth slowing down
development interactivity.

mkfs silently truncates "zkapissuer-database" to "zkapissuer-datab" and
everything falls apart.

The point is this is where PaymentServer's persistent state goes.  That
includes vouchers but might include more stuff too.

The hardware modules can now configure this fileSystem in a way appropriate
for themselves and the issuer module can enable that configuration when it is
enabled itself.

It looks like this may have been originally copied from a newer nixpkgs
since it wasn't in our nixpkgs fork.

The differences I can see:
- Details of `sudoer` file, some of which appear to be duplicates.
- `jq` and `gnumake` are not on the system path
- `vagrant` user is in group `users` instead of `vagrant`.

There is no swap to use but (a) try the setting anyway and (b) maybe there
will be at some point.