Fix a potential NPE

git-svn-id: https://svn.apache.org/repos/asf/aries/trunk@1601414 13f79535-47bb-0310-9956-ffa450edef68
Define the versioning plugin as an execution in the parent pom.  It can thus be removed from ALL the other poms.

git-svn-id: https://svn.apache.org/repos/asf/aries/trunk@1601415 13f79535-47bb-0310-9956-ffa450edef68