Check secret resource is changed before updating it

[jenting]

The Vault operator generates the k8s secret resource from the vault CR. Once the secret generated, the vault operator reconcile the Vault CR and updating the secret even the secret resource if the same.

We should compare the secret resource is changed before updating the secret. If the secrets without changing, bypass the update secret operations. This could decreasing the unnecessary kube-server Update API call as well as decreasing the ETCD DB size increase.