Prevent local m2 repo nuxeo distrib snapshot accumulation

Even if we use the build-helper-maven-plugin during the package phase to cleanup old snapshot.
This cleanup only happens if we build the tomcat nuxeo distribution.

On some slaves or dev machine we only run functional tests that have the Nuxeo distribution as dependency.
In this case the cleaning is not done and the zip packages keep accumulating.

The same behavior happens to other artifacts that are not locally build (but the Nuxeo tomcat distrib is huge).

We should provide cleaning scripts.