RC auto staging checks out SVN even on non-release builds

The auto-staging mechanism for release candidates checks out the staging repository for release candidates even when there is no release build going on. This is a bit annoying because it requires that people that want to build auto-staging-enabled projects need to have SVN installed.

This happens during SNAPSHOT CI builds as well - pretty annoying. I have to declare -Ddisable-rc-auto-staging in the {{Jenkinsfile}}s to get around this.

Enabling the auto-staging profile by adding it to the Maven Release Plugin releaseProfiles would work. But then projects that do not use it have to override the releaseProfiles setting to remove it again or if we do not make it the default, then projects that use it have to override releaseProfiles to add it.

Adding a -Dxxx to the arguments setting does not seem to be a great idea because it is more common that a developer would like to pass additional arguments than a developer wanting to pass additional release profiles. And developer-set arguments would not be accepted anymore if we hard-set the arguments in the release plugin - been there, done that, was not good.