Update tools/maven handling in 8.x to match master

The master branch has had its handling of maven changed such that the maven jars are no longer part of the source repo. This results in hassles when the 8.x branch is checked out in a local git repo, as the maven jars pulled down by the master build are now treated as untracked files by git.

Task is to make 8.x work like master so these files will be ignored by git.