Fail when image is bigger than the volume

Fail when image is bigger than the volume

When creating a new volume from a qcow2 image stored in glance, we will
be given the physical size of the image instead of the virtual size.
Most drivers will convert that image to raw after downloading for
resizing it to the requested volume size afterwards.

If the virtual size of the image is bigger than the requested one, the
resulting volume might end up being unusable after the resize even
though the creation went good.

This patch will make the volume creation fail if the virtual size of
the image exceeds the one of the requested volume.

Closes-Bug: #1235358
Change-Id: I254cd9e3acf5d9eb7eb913b37d27a14e97568dec