lxd/storage/utils: Adds checks to ImageUnpack before enlarging volume
lxd/storage/utils: Adds checks to ImageUnpack before enlarging volume

Ensures that we don't allow an oversized image to enlarge a volume beyond volume's specifie size.

Signed-off-by: Thomas Parrott <6b778ce645fb0e3dde76d79eccad490955b1ae74@canonical.com>

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