title: Jenkins doesn't fetch the correct Gerrit branch
body: <p>I want jenkins to test the code for review. The jenkins job is started on a push to refs/for/master but it tries to build the origin/master branch and not the refs/changes/XX/X/X branch. Has somebody an idea what i did wrong?</p>
  
  <p>Log from jenkins:</p>
  
  <pre><code>Triggered by Gerrit: http://localhost/13
  Building on master in workspace 
  /var/lib/jenkins/jobs/CI-JoysteerLogApi/workspace
  Checkout:workspace / /var/lib/jenkins/jobs/CI-JoysteerLogApi/workspace - hudson.remoting.LocalChannel@28071488
  Using strategy: Default
  Last Built Revision: Revision f604c6257923d4231b74573528d0116e0b52dc64 (origin/master)
  Fetching changes from 1 remote Git repository
  Fetching upstream changes from ssh://jenkinsCI@192.168.5.20:29418/JoysteerLogApi.git
  Commencing build of Revision f604c6257923d4231b74573528d0116e0b52dc64 (origin/master)
  Checking out Revision f604c6257923d4231b74573528d0116e0b52dc64 (origin/master)
  </code></pre>
  
  <p>Git config:</p>
  
  <pre><code>Repository URL: ssh://user@localhost:29418/Project.git
  Refspec: $GERRIT_REFSPEC
  Branches to build: $GERRIT_BRANCH
  </code></pre>
  
  <p>Gerrit Trigger config:</p>
  
  <pre><code>Gerrit Project:
    Type: Plain
    Pattern: Project
    Branches:
      Type: Path
      Pattern: **
  </code></pre>