Create test case for dispute with app

[matthiasgeihs]

Location

client

Problem

The Adjudicator.Withdraw functionality waits for a dispute to be over before it concludes the channel state. This is tested for no-app channels. However, if a channel has an app, the dispute period is prolonged and the function must wait for an additional challenge duration before it can settle the channel state. No current test covers that case.

Proposal

Add a test case where the withdraw functionality is tested for app channels in case of a dispute.