cmd trace can be ended twice

It's possible for a request cancel to race with a response completion. When this happens there is a gap on the memdclient side between releasing the request lock and setting request completion to 1. The same is effectively true for the opposite also, after we have handled cancelling a request we can continue handling it as an error case in the memdclient. The effect of this is that we end up cancelling the net and cmd traces twice.