Reject inconsistency in transactions with same nonce

[dasanra]

We currently addressed the issue that affected transactions pending that have the same nonce. This can be a handful use case for some teams that want to overwrite a transaction they don't want to execute anymore.

After this change some inconsistencies are left that require further refactor. If two transactions with the same nonce are created and one of them gets a reject signature, this reject signature will be shown in both transactions. This happens because cancel transactions are related using the nonce instead of txHash, so the interface is not able to distinguish correctly which is the correct transaction.

We should check all the places where we relate transactions by nonce in order to prevent behaviors like this

[rmeissner]

If two transactions with the same nonce are created and one of them gets a reject signature, this reject signature will be shown in both transactions

This is expected behaviour for me right now

[tschubotz]

I think so too. Also, with #820 this should be fixed. Hence, I'd close this ticket for now. Please reopen in case there are objections.