Fix Ffactor construction with surface adjacency

[mdahlhausen]

Pull request overview

• Fixes UA calculation failure in test_bldg_13 #1829
• The error is caused by a surface adopting the construction of the adjacent surface, an FfactorGroundFloor construction, which does not have a U factor, so the surface.uFactor.get call fails.
• The model is malformed - to surfaces are adjacent, but one is assigned an FfactorGroundFloor construction. That ought to not be a valid construction for surfaces with another surface as the boundary condition.

Fix:

• Delete the FfactorGroundFloor construction assignment for the two adjacent surfaces; that construction was only used on those two surfaces. Have the adjacent surfaces use the default construction.
• Add a check to make sure the optional U factor is initialized.

Pull Request Author

• Method changes or additions
• Resolved yard documentation errors for new code (ran bundle exec rake doc)
• Resolved rubocop syntax errors for new code (ran bundle exec rake rubocop)
• All new and existing tests passes

Review Checklist

• Perform a code review on GitHub
• All related changes have been implemented: method additions, changes, tests
• Check rubocop errors
• Check yard doc errors
• If fixing a defect, verify by running develop branch and reproducing defect, then running PR and reproducing fix
• CI status: all green or justified