[ACS44] Cherry-pick for CLOUDSTACK-4549

[Wido den Hollander]

Hi Daan,

Could you please cherry-pick 355f1a2a7599f25771f390f7dba2f8659dbe8fa6 
for me into the 4.4 branch?

This fixes CLOUDSTACK-4549 [0] where users couldn't create a new volume 
from a RBD snapshot.

I tested it on my local environment where the agents run the code from 
4.4-forward with my patch and it works.

Wido

[0]: https://issues.apache.org/jira/browse/CLOUDSTACK-4549