Add list namespace permissions to clusterrole
Add list namespace permissions to clusterrole

Should fix the following error

```
E0823 09:42:43.052518       1 reflector.go:134] pkg/mod/k8s.io/client-go@v2.0.0-alpha.0.0.20181213151034-8d9ed539ba31+incompatible/tools/cache/reflector.go:95: Failed to list *v1.Namespace: namespaces is forbidden: User "system:serviceaccount:vault:vault-operator" cannot list resource "namespaces" in API group "" at the cluster scope

E0823 10:13:47.130452       1 reflector.go:251] pkg/mod/k8s.io/client-go@v2.0.0-alpha.0.0.20181213151034-8d9ed539ba31+incompatible/tools/cache/reflector.go:95: Failed to watch *v1.Namespace: unknown (get namespaces)

```
banzaicloud/bank-vaults,banzaicloud/bank-vaults