Bugfix for autosizing when detailed performance capacity fractions are provided

[yzhou601]

Pull Request Description

The autosizing to convert design condition load to rated condition capacity (47F) is based on the 47F maximum capacity fraction, which is not correct. It should apply the nominal capacity fraction (which is 1.0).
cc @jonwinkler

Checklist

Not all may apply:

• Schematron validator (EPvalidator.xml) has been updated
• Sample files have been added/updated (openstudio tasks.rb update_hpxmls)
• Tests have been added/updated (e.g., HPXMLtoOpenStudio/tests/test*.rb and/or workflow/tests/test*.rb)
• Documentation has been updated
• Changelog has been updated
• openstudio tasks.rb update_measures has been run
• No unexpected changes to simulation results of sample files

[yzhou601]

	case8	case11
design temperatgure	6.62	6.62
outdoor temp	maximum capacity fraction	maximum capacity fraction
67	1.641	2.001
47	1.216	1.483
17	0.913	1.101
5	0.867	1.049
slope (17F to 5F)	0.003833333	0.004333333
fraction design to nominal (interpolated)	0.873133333	1.055933333
fraction design to max 47F	0.718037281	0.712025174
design load	55527.13901	55527.13901
rated capacity EXPECTED	63595.25732	52585.83781
rated capacity ACTUAL	77331.8329	77984.79748
capacity at 5F maximum speed EXPECTED	55137.0881	55162.54387
capacity at 5F maximum speed ACTUAL	67046.69912	81806.05255

These two cases run the same home with different heat pump detailed performance inputs (capacity fractions), using autosizing. The design temperature is 6.6F but the capacities at 5F after hvac sizing are very different, which is caused by this issue. This PR fixed it and now gave numbers very close to expectations.