Make sure coin production branch is same that the one used in real life

This is a action point from Qt release team LL meeting. We need to tag coin version used to create release packages. At the moment this is (almost) impossible because there is usually some cherry-picks at the top of production branch and that's why we can't tag release in coin git repository. So we need to change our way of working to support that requirement. It means COIN production branch must match to one used in real CI system and those cherry-picks must be done somehow differently.