Ansible launcher: log exit code from each builder

Change-Id: I6871c2b9ea9da025bcb60a5b6e25a04d442308bf
diff --git a/zuul/ansible/library/zuul_runner.py b/zuul/ansible/library/zuul_runner.py
index 784c7fd..a230448 100644
--- a/zuul/ansible/library/zuul_runner.py
+++ b/zuul/ansible/library/zuul_runner.py
@@ -68,7 +68,8 @@
                 break
             console.addLine(line)
 
-    ret = proc.wait()
+        ret = proc.wait()
+        console.addLine("[Zuul] Exit code: %s\n" % ret)
     return ret