RigSimulationInputTool-Test: discarding return value of function

[jonjenssen]

Update tests to use return value, disable warning, or remove [[nodiscard]] attribute.

E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(1909): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(1959): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2006): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2062): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2123): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2422): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2467): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2523): warning C4834: discarding return value of function with [[nodiscard]] attribute
E:\src\ResInsight\ApplicationLibCode\UnitTests\RigSimulationInputTool-Test.cpp(2580): warning C4834: discarding return value of function with [[nodiscard]] attribute