[libvirt] "Only raw volumes are supported"

[Richard Laager]

I think the two commits below need to be reverted. This is now 
preventing me from creating ZFS volumes (and presumably would block 
creating LVM volumes too). I don't know how this passed my testing 
before and isn't working now, but that seems to be the case.

When I run `virsh vol-create-as --pool=zfs --name=sparse1 --capacity=1G 
--format=raw`, target.format is 0 (VIR_STORAGE_FILE_NONE).

Also note that the equivalent code in RBD came in a commit with more 
code. So I'm thinking I was on the wrong track with these two patches.

commit bb5f2dc91f43f48ff726aa589bdac546738d2980
Author: Richard Laager <rlaager at wiktel.com>
Date:   Tue Mar 15 01:17:35 2016 -0500

     zfs: Only raw volumes are supported

commit 6682d6219d4595b51f06867e0c30e7efd745f682
Author: Richard Laager <rlaager at wiktel.com>
Date:   Tue Mar 15 01:17:34 2016 -0500

     logical: Only raw volumes are supported

-- 
Richard