TestXMRTakerCancelOrRefundAfterKeyExchange flaky
The recently added test, `TestXMRTakerCancelOrRefundAfterKeyExchange`, is flaky. The problem is this code:
```go
			count, err := ec.PendingTransactionCount(ctx) //nolint:govet
			if err != nil {
				t.Errorf("failed to get pending tx count: %s", err)
				return
			}

			if count > 0 {
				// the newSwap tx is in the mempool, shut down the nodes
				cancel()
				t.Log("cancelling context of Alice's and Bob's servers")
				return
			}
```
Multiple packages are being tested concurrently and the pending transaction that is found is sometimes an unrelated transaction that happens before the `newSwap` transaction that it is looking for is created. Then the `newSwap` transaction never gets created because the context is cancelled first. The swap ends up with the status of `aborted`.