Fix massive leak experienced by tower_opt repo

Slight change in behavior found in test_vartree.py looks to be innocuous, the test has been updated to more explicitly verify what I think is equivalent required behavior.

pkg_res_factory change is bogus workaround required to pass tests when tower_opt has been installed.

caseiteratordriver change fixes collateral pickling damage.

This fixes the worst leak, there is still a leak when a VarTree is connected to a VarTree.