Previously, the zfs binaries were put in $out/sbin where the stage-1
patchelf wouldn't fix them up. This would fail the allowedReferences
test.
Move the zfs binaries to $out/bin.
When nixos-rebuild grabs a new kernel, it will build new spl/zfs
modules, which will change the service. On completion nixos will try and
restart the services which will try and import pools again, and
generally will fail.
The pools are already imported, we don't need to do it again..
