[Libguestfs] [PATCH v3] v2v: -o rhv-upload: Use Unix domain socket to access imageio (RHBZ#1588088).

[Richard W.M. Jones]

v2 was here:
https://www.redhat.com/archives/libguestfs/2018-June/msg00109.html

v3:

- Added/fixed all suggestions from Nir in previous review.

Q: I wasn't sure if we still need the "UnsupportedError" class so I
left it in.

Q: Does the Unix socket always have the same name?  What happens if
there's more than one transfer happening?

I tested this both ways, and it worked both ways.  The output when the
optimization is used looks like this:

  disk.id = '45d1a30c-82c0-4b00-8bfb-c4d628dbf72d'
  hw_id = '81F716C4-4D19-CB35-82F7-94C691189FEB'
  host.id = '87daa64d-b27e-4336-a156-973544be708b'
  transfer.id = '5ffea7fa-966c-42a4-a77a-3efd6dc45c34'
  imageio features: flush=True trim=False zero=True unix_socket='\x00/org/ovirt/imageio'
  optimizing connection using unix socket '\x00/org/ovirt/imageio'

Rich.