Add job dependencies to status.json

Adding the job dependencies will make it possible to render the job
graphs as real graphs. In example one could think of a details popup
when clicking on a details link.

Change-Id: Id9c376a47b28ff022eb69f957c18791d7130daf1
diff --git a/zuul/model.py b/zuul/model.py
index 436a9c8..ad0e8d1 100644
--- a/zuul/model.py
+++ b/zuul/model.py
@@ -1695,6 +1695,7 @@
 
             ret['jobs'].append({
                 'name': job.name,
+                'dependencies': list(job.dependencies),
                 'elapsed_time': elapsed,
                 'remaining_time': remaining,
                 'url': build_url,