Fix tests in CI by using local maven repo in target/

* about 150 tests in currently failing in CI due to failure when acquiring some file from ~/.m2.

* using clean repo for every build (instead of the
  shared one in ~/.m2) fixes the failing tests in CI

* having the local repo in target/ also greatly
   improves the isolation of the tests. They are
   less dependent on the current state of ~/.m2 on
   the particular machine

* with these changes, there is only remaining failure that does not seem to be related to this: https://jenkins.mw.lab.eng.bos.redhat.com/hudson/job/jbpm-psiroky-testing/ (I cloned the job and ran with the changes in this PR)

* this solution is not 100 % ideal as the same xml file/code is in three places. However, I could not think of any easier/better way. I will try to find an easy way to specify this config in one place so it can be shared by other modules and create another PR if I find such solution.