Account for collapsed units when determining geometry variables for infiltration calculation

[aspeake]

Pull Request Description

Fixes how geometry variables (building ffa, building volume, and building exterior wall area) are calculated in the Airflow.rb measure when minimal_collapsed == True. The "collapsed" units were not originally accounted for when determining these variables, influencing the calculated leakage area at each unit. This changes the infiltration and HVAC sizing in SFA buildings, and most likely MF buildings as well.

Checklist

Not all may apply:

• Unit tests have been added or updated
• All rake tasks have been run, and pass
• Documentation has been modified appropriately
• Any new options are added to project_testing
• project_testing runs without any failures
• No unexpected regression test changes
• All tests are passing (green) on circleci
• The changelog has been updated appropriately
• This branch is up-to-date with master

For more information on how to perform these checklist items, see the documentation's Advanced Tutorial.