Add dco-license job

This is a follow up to the previous commit, here we are adding a job
called dco-license which only runs on localhost (zuul-executor).

Change-Id: Id624160930b80b5b37a8e05b000106c16fef64e0
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

playbooks/dco-license/run.yaml

@@ -0,0 +1,7 @@
+- hosts: localhost
+  tasks:
+    - name: Run validate-dco-license role
+      include_role:
+        name: validate-dco-license
+      vars:
+        zuul_work_dir: "{{ zuul.executor.work_root }}/{{ zuul.project.src_dir }}"

zuul.yaml

@@ -1,6 +1,14 @@
 # Shared jobs that are generally applicable to everyone
 # Assumes a 'base' job defined elsewhere
 
+- job:
+    name: dco-license
+    description: |
+      A job to validate all new commits have been signed using --signoff.
+    run: playbooks/dco-license/run.yaml
+    nodeset:
+      nodes: []
+
 - job:
     name: unittests
     abstract: true