diverted stores are only necessary when the logical store paths of
objects matter for the test itself, such as for derivation hashes,
substitution from golden sample nars, or actual tests of the store
diversion functionality. all other tests can use undiverted stores
to run, especially since only linux can build in diverted a store.
Change-Id: I62f0907bdef9961609af22b610195fcec54c1e57
eldritch horrors
b34f136f10