mark_as_modified doesn't work correctly with scale parameters

[anth-volk]

For example, say I want to take an Alabama state income tax bracket and run the mark_as_modified() method upon it. It appears that gov.states.al.tax.income.rates[1] doesn't recognize gov.states.al.tax.income.rates as its parent, thereby preventing mark_as_modified() from recursing further up the tree.

The downstream impact of this is that, if I wanted to use cached values while calculating (assuming all other current issues we have with state-level caching were gone), the simulation wouldn't correctly recurse all the way to gov.states, thereby giving an erroneous output for household_state_income_tax.