Extend Close() capabilities to actually mimic real interfaces

[fako1024]

Right now the flow for a mock interface slightly differs from a real one in the sense of opening / closing (because the source potentially has to be populated) so that in various scenarios it might be difficult to simulate repeated open() / close(). For better usability, this flow could be improved.

DoD

• Assess current limitations (add tests)
• Adjust behavior / flow to mimic real life behavior
• Adjust documentation if required