integration test: snapshot improvements tests

1. Test - Snapshot on linux VM root disk

Signed-off-by: sanjeevneelarapu <sanjeev.neelarapu@citrix.com>
Merge remote branch 'upstream/master'
Merge branch 'master' of https://github.com/CloudStack-QA/incubator-cloudstack
Merge branch 'master' of https://github.com/CloudStack-QA/incubator-cloudstack
marvin integration test: snapshot improvements
2. test snapshot on windows vm root volume