storage: Fix volume cloning for logical volume.
storage: Fix volume cloning for logical volume.

When creating a logical volume with virStorageVolCreateXMLFrom,
"qemu-img convert" is called internally if clonevol is a file volume.
Then, vol->target.format is used as output_fmt parameter but the
target.format of logical volumes is always 0 because logical volumes
haven't the volume format type element.

Fortunately, 0 was treated as RAW file format before commit f772b3d9,
so there was no problem. But now, 0 is treated as the type of none,
qemu-img fails with "Unknown file format 'none'".

This patch fixes this issue by treating output block devices as RAW
file format like for input block devices.

Signed-off-by: Atsushi Kumagai <39d7451d585f773af30891a53feb06e85def8e7d@mxc.nes.nec.co.jp>

eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,elmarco/libvirt,zippy2/libvirt,datto/libvirt,VenkatDatta/libvirt,agx/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,andreabolognani/libvirt,agx/libvirt,olafhering/libvirt,taget/libvirt,jardasgit/libvirt,jardasgit/libvirt,eskultety/libvirt,zhlcindy/libvirt-1.1.4-maintain,cbosdo/libvirt,libvirt/libvirt,VenkatDatta/libvirt,jardasgit/libvirt,cbosdo/libvirt,shugaoye/libvirt,eskultety/libvirt,VenkatDatta/libvirt,rlaager/libvirt,fabianfreyer/libvirt,libvirt/libvirt,andreabolognani/libvirt,elmarco/libvirt,nertpinx/libvirt,crobinso/libvirt,crobinso/libvirt,shugaoye/libvirt,rlaager/libvirt,shugaoye/libvirt,agx/libvirt,jfehlig/libvirt,zhlcindy/libvirt-1.1.4-maintain,nertpinx/libvirt,taget/libvirt,fabianfreyer/libvirt,taget/libvirt,nertpinx/libvirt,zippy2/libvirt,fabianfreyer/libvirt,VenkatDatta/libvirt,VenkatDatta/libvirt,zippy2/libvirt,datto/libvirt,elmarco/libvirt,zippy2/libvirt,agx/libvirt,fabianfreyer/libvirt,agx/libvirt,jfehlig/libvirt,crobinso/libvirt,andreabolognani/libvirt,libvirt/libvirt,elmarco/libvirt,taget/libvirt,jardasgit/libvirt,rlaager/libvirt,nertpinx/libvirt,zhlcindy/libvirt-1.1.4-maintain,datto/libvirt,crobinso/libvirt,jardasgit/libvirt,eskultety/libvirt,andreabolognani/libvirt,fabianfreyer/libvirt,rlaager/libvirt,taget/libvirt,olafhering/libvirt,shugaoye/libvirt,olafhering/libvirt,elmarco/libvirt,olafhering/libvirt,shugaoye/libvirt,eskultety/libvirt,datto/libvirt,cbosdo/libvirt,jfehlig/libvirt,nertpinx/libvirt,datto/libvirt,cbosdo/libvirt,andreabolognani/libvirt,jfehlig/libvirt,rlaager/libvirt