Keep better tabs on secondary tables.

We had some places (NatController) where routes were being set
but not accounted for in the number-of-routes talley so we
could end up thinking the table was empty and not clean up
after ourselves properly.

Also consolidated constants.

bug:5917475
Change-Id: I98a41d433e1d4b4ca6692fb2328e2c9afc828145