Merge pull request #245 from axsh/feature-volume-localstore

Fix issues from smoke test.
mussel,helper: make sure to get value of first level key.
Merge pull request #246 from axsh/fix-mussel-document-pair

mussel,helper: make sure to get value of first level key.
fix validation only when runs not null.
fix nil error by copying not null attributes properly.
add "PUT /instances/i-xxx/volumes/vol-xxxx/backup" API endpoint.
add volume backup support to hva.
disable async update for resource attributes.
change volume API response to return addtional values.