Fix for qcow2 volume resize
Fix for qcow2 volume resize

If qcow2 volume has bigger size than specified for the volume with
the attribute 'capacity', qemu-img fails to shrink such image.

- do not fail if the image cannot be shrinked to specified size

Change-Id: I8560e04657eb6570c43ebe07ddd5aa4975de9aec
Closes-Bug:#1546635

stackforge/fuel-devops,stackforge/fuel-devops