[sheepdog] [PATCH] dog: fix improper typed 'ret' in 'vdi create'

[Liu Yuan]

On Tue, Jan 21, 2014 at 09:49:00PM +0800, Liu Yuan wrote:
> 'ret' is unsigned then never get < 0 even in error case, so for a wrong size, we
> will proceed to create an invalid vdi.
> 

Applied

Yuan