Use tests to check system configuration

[nachtmaar]

The acceptance tests should be used to test which network backends and which network backend options work on the system.
This gives the user the possibility to choose a good network backend.

Moreover, this mechanism could be used to check whether a given scenario and image work correctly with MiniWorld.

I guess we need to provide more CLI switches to purest such that these parameters can be supplied to the test environment.

>>> pytest --some-args some_tests
image ok
iproute2 network backend error
pyroute2 network backend ok