Functional test -- genuine coin flip

Test the genuine coin flip logic (i.e. responsiveness_threshold and gradient leadership)

suggested scenarios
Given a situation where the step is Step::GenuineFlip,

• most leader comes back first. We must use his bit

• most leader comes back right at the end of responsiveness_threshold. We must use his bit

• most leader comes back right after responsiveness_threshold and second most leader comes back on time. We must use second most leader bit

• a third minus one most leader nodes don't come back at all. We must use next most leader's bit