If a user originally does not setup the alternatives entry for their cdap configuration on initial install, and then some time later decide to upgrade, they may find their configuration is wiped out. We should add a warning before the "upgrade cdap packages" step to doublecheck this.
The way it should work:
1. cdap packages own /etc/cdap/conf.dist/cdap-site.xml.
2. user creates /etc/cdap/conf.xxx
3. using alternatives user points link "/etc/cdap/conf" to /etc/cdap/conf.xxx
Then, when upgrading packages, /etc/cdap/conf.dist/cdap-site.xml is upgraded, but it doesn't matter.