CLOUDSTACK-9529: Cleanup resources after marvin test completes

- Cleans up volumes, snapshots and VM after running test_snapshots

Signed-off-by: Rohit Yadav <rohit.yadav@shapeblue.com>

test/integration/smoke/test_snapshots.py

@@ -196,6 +196,7 @@ class TestSnapshotRootDisk(cloudstackTestCase):
             account=self.account.name,
             domainid=self.account.domainid
         )
+        self.cleanup.append(snapshot)
         self.debug("Snapshot created: ID - %s" % snapshot.id)
 
         snapshots = list_snapshots(