Clean function removed from mockService interface

[mboudreau]

in the latest version, 2.0.0, it seems that the clean function has been removed, again. This was particularly useful for me that would setup a particular interaction once in the beforeAll, run several tests on it, then clean the interactions up in the afterAll function.

Without this clean function, we would have to duplicate a lot of code into the tests themselves so that it can work with the run function.

[bethesque]

Feel free to add it back in in a PR, not sure why it was removed.