Functional tests: have all duplicated code in only one place

In the functional tests files (*.py), a lot of lines of code is duplicated. Refactor it so it is included or imported.

Typical use case: changing the IP address of the host on which running the tests is painful.

Python resources:

1. How to import other Python files
2. Importing files from different folder
3. Un gros guide bien gras sur les tests unitaires en Python, partie 2
4. Leverage setUpClass, tearDownClass, setUpModule and tearDownModule see Class and Module fixture ; which order is clearly explained in Fixture syntax and Flow reference