mussel: add first local-volume-instance scenario.
mussel: handle sudo command in an instance.
mussel: add -P option to df command.
mussel: split remote command set.
mussel: make sure to unmount disk and show disk usage.
mussel: add time command.
mussel: fix string escape.
mussel: change default blank_volume_size from 1G to 10M.
mussel: enable to set blank_volume_size with shell-variable/env-variable/.musselrc.
Merge pull request #295 from axsh/localvolume-test-scenario

Localvolume test scenario