Add scenario test of instance/volume snapshot

This test is for snapshotting an instance/volume
and attaching the volume created from snapshot
to the instance booted from snapshot.
The following is the scenario outline:
1. Boot an instance "instance1"
2. Create a volume "volume1"
3. Attach volume1 to instance1
4. Create a filesystem on volume1
5. Mount volume1
6. Create a file which timestamp is written in volume1
7. Unmount volume1
8. Detach volume1 from instance1
9. Get a snapshot "snapshot_from_volume" of volume1
10. Get a snapshot "snapshot_from_instance" of instance1
11. Boot an instance "instance2" from snapshot_from_instance
12. Create a volume "volume2"  from snapshot_from_volume
13. Attach volume2 to instance2
14. Check the existence of a file which created at 6. in volume2

Change-Id: If8eef9c8c4415b8658ac1b13dc2e114dc22378b4
Fixes: bug #1203637
Merge "Add scenario test of instance/volume snapshot"