Add tests for MITM components and other PyRDP features

[xshill]

So I think we could definitely use some tests in the whole project to help us identify potential bugs. However, at this point, spending time writing tests is quite a daunting task and not necessarily the most fun thing either.

However, as we work on a component to improve or fix it, I think it would be worth spending time implementing tests for that component so that eventually we end up having tests for most components / features.

This is a bit more of an abstract issue to describe the overall goal but more concrete issues like "Add tests for DeviceRedirectionMITM" for example should be opened as the opportunities arise.

[xshill]

References for implementation:

• Logging calls: https://stackoverflow.com/a/34920727
• Filesystem calls: https://stackoverflow.com/questions/19672138/how-do-i-mock-the-filesystem-in-python-unit-tests