Provide API to close secure storage for CDH

[Xynnn007]

Currently we have Secure Storage API for CDH to mount an encrypted storage media to the target. We also need an API to close a given secure storage. Thus we need to consider

1. how to index each secure storage instance
2. how to record the opened secure storage's state
3. impl an api to get the info about the current opened secure storages
4. impl an api to close the specified secure storage instance