e2e SecurityContext tests wrong volume dir

The volume directory is not guaranteed to be /var/lib/kubelet
for a conforming implementation of Kubernetes.  Add --volume-dir
and an internal shim

hack/verify-flags/known-flags.txt

@@ -364,6 +364,7 @@ upgrade-target
 use-kubernetes-cluster-service
 user-whitelist
 verify-only
+volume-dir
 volume-plugin-dir
 volume-stats-agg-period
 watch-cache