Whenever the nixos-taskserver tool was invoked manually for creating an
organisation/group/user we now add an empty file called .imperative to
the data directory.
During the preStart of the Taskserver service, we use process-json which
in turn now checks whether those .imperative files exist and if so, it
doesn't do anything with it.
This should now ensure that whenever there is a manually created user,
it doesn't get killed off by the declarative configuration in case it
shouldn't exist within that configuration.
In addition, we also add a small subtest to check whether this is
happening or not and fail if the imperatively created user got deleted
by process-json.
Signed-off-by: aszlig <aszlig@redmoonstudios.org>