hmp: Update info vnc

The QMP query-vnc interfaces have gained a lot more information that
the HMP interfaces hasn't got yet. Update it.

Note the output format has changed, but this is HMP so that's OK.

In particular, this now includes client information for reverse
connections:

-vnc :0
(qemu) info vnc
default:
  Server: 0.0.0.0:5900 (ipv4)
    Auth: none (Sub: none)

  (Now connect a client)

(qemu) info vnc
default:
  Server: 0.0.0.0:5900 (ipv4)
    Auth: none (Sub: none)
  Client: 127.0.0.1:51828 (ipv4)
    x509_dname: none
    sasl_username: none

-vnc localhost:7000,reverse
(qemu) info vnc
default:
  Client: ::1:7000 (ipv6)
    x509_dname: none
    sasl_username: none
  Auth: none (Sub: none)

-vnc :1,password,id=pass -vnc localhost:7000,reverse
(qemu) info vnc
default:
  Client: ::1:7000 (ipv6)
    x509_dname: none
    sasl_username: none
  Auth: none (Sub: none)
rev:
  Server: 0.0.0.0:5901 (ipv4)
    Auth: vnc (Sub: none)
  Client: 127.0.0.1:53616 (ipv4)
    x509_dname: none
    sasl_username: none

This was originally RH bz 1461682

Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20170711154414.21111-1-dgilbert@redhat.com
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
