Fix false warnings from getSatTemperature

[mjwitte]

Pull request overview

• Fixes missing initialization of ErrorFlag in RefrigProps::getSatTemperature which was causing erroneous warnings. Noticed this because unit test VRF_FluidTCtrl_VRFOU_Compressor failed locally on Windows with an uninitialized variable exception after merging in FluidProperties API #10616.

This gets rid of the err diffs and fixes the unit test (and maybe others).

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[rraustad]

Ran this branch in debug mode and unit tests ran to completion. This looks good.

[rraustad]

ReturnValue would always get set, ErrorFlag may not get set and may or may not trip the warning. This should fix the unit test issue.