Further nova smoketest modifications:

9. Snapshot vm to volume
10. boot from snapshoted instance-volume(with tests if it accesible from vm)
11. create volume from image
12. boot from volume created from image(with tests if it accesible from vm)
13. snapshot delete
14. volume delete

Also:
1. Tests skip feature for steps 11,12 due to a Cinder Bug 1183283
2. Comments about possible issues with nova Bug 1008622
3. Some improvements in order to make smoketest more stable in case of multiple reruns
4. Minor typos fixed