RHEL's/Fedora's virsh has no --prealloc-metadata

The --prealloc-metadata option used when creating a volume by virsh
does not exist on Fedora or RHEL.

Change-Id: I4424e0aafa59553223c31b2e964d9f94a960d92c
Merge "RHEL's/Fedora's virsh has no --prealloc-metadata"