Add tests for TeosDaemon

[bigspider]

After the refactoring of teosd.py in #202, all the code that handles the initialization of the tower's components, starting the services and clean teardown is contained in the TeosDaemon class.

This should allow now to have some unit tests for the various parts of the code of the class.

Things to consider:

• a further refactoring of the methods might be needed to improve testability
• we might want to have some form of dependency injection in order to be able to mock the various components during unit tests.