Add tests for engine request canceling
Add tests for engine request canceling

Still dont particularly like that we are reaching into
engine._http_session to do this, but the only other option I see
is to would be to mock out import.gi.Soup.Session which seems
equally as error prone
[endlessm/eos-sdk#2508]

endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib,endlessm/eos-knowledge-lib