[Libguestfs] [PATCH] launch: appliance: Add custom parameters last.

[infernix]

 > From: "Richard W.M. Jones" <rjones redhat com>
 > This allows custom parameters to modify parameters added by
 > libguestfs, eg. by doing:
 >  -set drive.hd0.file=rbd:foo/bar

This works for recent versions of QEMU. The way to use this is:

guestfish
<fs> add-drive /dev/null
<fs> config -set drive.hd0.file=rbd:pool/volume
<fs> run

This will probably work for more types (sheepdog, iscsi et al), but with 
the caveat that the libguestfs layers are bypassed so you'll *always* 
end up directly accessing the disk in rw mode.