Fix AttributeError in executor client

We were inadvertantly redifining the item variable which caused
this error:

  AttributeError: 'NoneType' object has no attribute 'project_configs'

If a parent item happened not to have a layout yet.

Change-Id: I78a30cc95a1fe30e6aca3c44faae048191af2cdd
diff --git a/zuul/executor/client.py b/zuul/executor/client.py
index aaef34e..1c2d202 100644
--- a/zuul/executor/client.py
+++ b/zuul/executor/client.py
@@ -321,9 +321,9 @@
                     make_project_dict(project,
                                       job_project.override_branch))
                 projects.add(project)
-        for item in all_items:
-            if item.change.project not in projects:
-                project = item.change.project
+        for i in all_items:
+            if i.change.project not in projects:
+                project = i.change.project
                 params['projects'].append(make_project_dict(project))
                 projects.add(project)