nbd: enable use of TLS with nbd-server-start command

This modifies the nbd-server-start QMP command so that it
is possible to request use of TLS. This is done by adding
a new optional parameter "tls-creds" which provides the ID
of a previously created QCryptoTLSCreds object instance.

TLS is only supported when using an IPv4/IPv6 socket listener.

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Message-Id: <1455129674-17255-17-git-send-email-berrange@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/qmp-commands.hx b/qmp-commands.hx
index 020e5ee..9fb0d78 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -3825,7 +3825,7 @@
 
     {
         .name       = "nbd-server-start",
-        .args_type  = "addr:q",
+        .args_type  = "addr:q,tls-creds:s?",
         .mhandler.cmd_new = qmp_marshal_nbd_server_start,
     },
     {