Fix workingDir syntax.

@@ -108,7 +108,7 @@ spec:
 
         - name: try-helmfile
           image: quay.io/roboll/helmfile
-          working_dir: /tmp/git-storage/k8s-start-of-day
+          workingDir: /tmp/git-storage/k8s-start-of-day
           command: ["/tmp/k8s-bootstrap-scripts/check-mode", "helmfile", "/usr/local/bin/helmfile"]
           volumeMounts:
             - name: git-storage