Re-add back in --output=json to qemu-img command line
Re-add back in --output=json to qemu-img command line

Signed-off-by: Jon Ludlam <e7e3380887a8f95cc9dc4f0d51dedc7e849a287a@citrix.com>

jonludlam/vagrant-xenserver,jonludlam/vagrant-xenserver,jogjacamp/vagrant-xenserver-jc,jogjacamp/vagrant-xenserver-jc