Make rbd.libvirt_info parent class compatible

Rbd.libvirt_info function definition misses hypervisor_version argument added in change:
https://review.openstack.org/32379

Closes-Bug: #1233188
Change-Id: Ib68d743e783af0f6d82d2ba180869ee642e86050
Merge "Make rbd.libvirt_info parent class compatible"