Add inheritance path to zuul vars

This is temporary and undocumented -- I plan on reworking this into
structured data before finalizing the interface.  Will add
documentation then.

Change-Id: I4b9bceddf13e384c18bb27be8c493318c5af0fb4
diff --git a/zuul/executor/client.py b/zuul/executor/client.py
index 96fce2d..0e6544b 100644
--- a/zuul/executor/client.py
+++ b/zuul/executor/client.py
@@ -168,7 +168,8 @@
                            project=project,
                            tenant=tenant.name,
                            timeout=job.timeout,
-                           jobtags=sorted(job.tags))
+                           jobtags=sorted(job.tags),
+                           _inheritance_path=list(job.inheritance_path))
         if hasattr(item.change, 'branch'):
             zuul_params['branch'] = item.change.branch
         if hasattr(item.change, 'tag'):