I can't see any evidence that anyone else uses our nova-idmapshift
binary, and it adds a lot of complexity (flags we never call for
example). Move the code we do actually use into the privsep
directory and simplify our calls to it. Remove the extra binary
from our install and documentation.
Change-Id: Ibce28d20d166da154833376cf51f1877b829925e
blueprint: hurrah-for-privsep
3f7995f586