ACUMOS: Improve jenkins jobs for Acumos projects

ACUMOS: Improve jenkins jobs for Acumos projects

- Mirror branches from Acumos upstream project to Nordix.
- Do not force the git user.name to be the gerrit id.
  Git authorship can be independent from the
  gerrit review ownership now.
- Cache the repository on the Jenkins slave nodes
  when rebasing repositories.
- Make sure the commit hash in the local repo is the same
  as in nordix Gerrit and the same as the commit hash
  in the upstream gerrit.
- Decrease number of jobs required for project in Jenkins

Change-Id: I29ea8b9b2573b5d894246f47b537aeb61027f6f8