add mussel command "instance show_volumes" & "instance backup_volume".
set default guest_device_name for linux containers when migration 0014 runs.
fix unit test for help message.
Merge pull request #257 from axsh/feature-volume-localstore

Mussel test for "GET /instances/i-xxxxx/volumes" & "PUT /instances/i-xxxxx/volumes/vol-xxxx/backup"