fix result file path

[arun3688]

Related Issues

https://github.com/OpenModelica/OMPython/issues/206

Purpose

This PR fixes the result file path when resultfile location is provided by the user.

Usage

>>> from OMPython import ModelicaSystem
>>> mod = ModelicaSystem("C:/BouncingBall.mo", "BouncingBall")
>>> mod.simulate(resultfile="C:/OPENMODELICAGIT/BouncingBall_res.mat") // path provided by user
LOG_SUCCESS       | info    | The initialization finished successfully without homotopy method.
LOG_SUCCESS       | info    | The simulation finished successfully.
>>> mod.resultfile
'C:/OPENMODELICAGIT/BouncingBall_res.mat'
>>> mod.getSolutions()
('der(h)', 'der(v)', 'e', 'flying', 'foo', 'g', 'h', 'impact', 'time', 'v', 'v_new')
>>> mod.simulate(resultfile="test.mat") // providing only the file name 
LOG_SUCCESS       | info    | The initialization finished successfully without homotopy method.
LOG_SUCCESS       | info    | The simulation finished successfully.
>>> mod.getSolutions()
('der(h)', 'der(v)', 'e', 'flying', 'foo', 'g', 'h', 'impact', 'time', 'v', 'v_new')