GCC: unused warnings

[jeffro256]

This PR fixes 4 instances of -Wunused...

[moneromooo-monero]

At this point I'm unlikely to spend a lot of time thinking about it and fixing it well. So if people want to kill the warning, be my guest. I'd be better if people wanted to fix it properly instead of just killing the warning, but that's up to them.

[selsta]

@jeffro256 Can you keep the refreshed variable untouched and only add the comment? We can keep the warning as a reminder for someone to look into, if it stays unfixed for another year then we can decide what to do next with it.

Sorry for this huge discussion :)

[jeffro256]

@selsta done!