scenario test involving glance, cinder and nova functionalities

this is a new scenario test which tries to address a typical use
case where an image is uploaded in glance, later cloned into a
persistent volume in cinder, snapshotted and finally reused for new
instances; there is no attempt to check the actual image contents as
that would require ssh access

Change-Id: I55f0e5fdfc5aba8eb6c8f427ab0e672bb7dcd715
Merge "scenario test involving glance, cinder and nova functionalities"