This patch adds support to qcow2 formatted filesystem object storage by
instructing qemu-img to build them with preallocation=falloc whenever the
XML described storage <allocation> matches its <capacity>.  For all other
cases the filesystem stored objects are built with preallocation=metadata.
Signed-off-by: NWim ten Have <wim.ten.have@oracle.com>
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>