[libvirt] Improvements to the RBD storage backend
Hi,
After review by John Ferlan I'm sending a revised version of my earlier
patch which adds the fast-diff feature for RBD volumes.
Before the patch there is one small improvement which is later used
by the fast-diff feature.
The other is a bugfix where the #ifdef in the code wasn't requiring the
right version of librbd.
Wido