uci: do not commit on exit if there was no change done

We should not commit every time we exit from context because that can
take a long time. This remembers if some changes could have been done
and otherwise we do not commit on exit.
4 jobs for <span class="ref-name">no-commit-on-exit</span> in 39 seconds (queued for 5 seconds)
Status Job ID Name Coverage
  Test
passed #253057
python2

00:00:18

passed #253058
python3

00:00:19

 
  Pages
passed #253059
pages

00:00:19

 
  Deploy
passed pages:deploy

00:00:00