Unexpected errors when curves used for multiple objects

Issue overview

Current Behavior

This shows up as error which is then caught by standards and makes some measures fail.
(msg.logMessage.include?('[openstudio.model.Curve] This Curve, Object of type ') && msg.logMessage.include?(' has multiple parents. Returning the first.'))

Expected Behavior

Either the API should not let you assign same curve to multiple objects or it should not reflect doing so as an Error.

Steps to Reproduce

Running measure test related to this issue in ext reproduces it
https://github.com/NREL/openstudio-extension-gem/issues/95

Possible Solution

Decide if curve is resource or child and update all code to reflect that. Simpler fix it to keep it as a resource and just remove triggered errors.