[et-mgmt-tools] virt-manager: reuse "storage-file-size" upon "Back"

[Cole Robinson]

Jim Meyering wrote:
> I was surprised when "Back" clobbered a value I'd selected.
> I've confirmed that this patch fixes it.
> 
> FYI, the "size == None" test appears to be unnecessary, since
> the default is set in addhardware.py.  However, this might benefit
> from an added sanity check, in case the selected size is too small
> (currently, 0 is accepted).  But that is a separate issue.

Thanks, I've applied this:

http://hg.et.redhat.com/virt/applications/virt-manager--devel?cs=523f2f7501c6

- Cole