Add autotest to setup single node + running vm, afterwards extend to 3 node setup

[pploegaert]

Scenario:

• setup single node ovs
• add backend/vpool/import ubuntu image/startup qemu vm
• setup node 2/3 + add to cluster
• validate if: -- arakoons are properly extended -- vm is still running -- no errors occured during extend/after extend

Related to: https://github.com/openvstorage/alba-asdmanager/issues/155

[JeffreyDevloo]

I would rather take this up with: https://github.com/openvstorage/integrationtests/issues/273