Press OK one more time... after verifying scanned address

[jdlcdl]

While testing pr #651, I noticed that I needed to press the "OK" button a second time to leave the screen.

I thought it was related to a hardware issue at my end, but then I had problems reproducing it in 'dev' so I first reported this as an issue in pr 651.

Keith was able to reprovoke the error in 'dev', and I was eventually able to do the same.

• It's easier to reproduce on a slower pi0 than it is on a faster pi02w.
• It seems to have something to do with higher address indexes. Instead of scanning the 1st address, try the 91st address.
• It seems to have something to do with waiting to press "OK"... if you're quick, you won't provoke this behavior.

Keith resolved this with hardware "buttons.py" changes earlier... at least cutting and pasting a new version seemed to work for me... but a PR is still in waiting, so this issue is to provoke it.