ignore 'guest_device_name' API parameter from attach volume operation.
Revert "force reload volume and vif object when the association from instance is updated."

This reverts commit 12caffb72b7ee4154ffb65d11c697da854e7fc03.
fix that only scoped volumes will be backed up.
force reload instance association from volume always at validation.
Merge pull request #359 from axsh/fix-halted-instance-shared-vol

Fix validation error from volume model.
Merge pull request #351 from axsh/remove-guest-devname

Ignore 'guest_device_name' parameter from API.
Merge branch 'master' into feature-windows-handler