Make a new user that jenkins uses when it wants to do docker things.

playbooks/roles/tools_jenkins/defaults/main.yml

@@ -77,3 +77,5 @@ jenkins_tools_debian_pkgs:
     - python-pycurl
     - psmisc
     - mysql-client-core-5.6
+
+jenkins_tools_docker_user: 'jenkins-docker-proxy'

playbooks/roles/tools_jenkins/meta/main.yml

@@ -11,6 +11,9 @@ dependencies:
     jenkins_bundled_plugins: "{{ jenkins_tools_bundled_plugins }}"
     jenkins_debian_pkgs: "{{ jenkins_tools_debian_pkgs }}"
   # Needed to be able to build docker images. Used by Docker Image Builder Jobs.
+  - role: user
+    user_info:
+        - name: '{{ jenkins_tools_docker_user }}'
   - role: docker-tools
     docker_users:
-        - jenkins
+        - '{{ jenkins_tools_docker_user }}'