ui/vnc: don't check for SSF after SASL authentication on UNIX sockets

Although we avoid requesting an SSF when querying SASL mechanisms for a
UNIX socket client, we still mistakenly checked for availability of an
SSF once the SASL auth process is complete.

Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

ui/vnc-auth-sasl.c

@@ -628,7 +628,7 @@ void start_auth_sasl(VncState *vs)
             goto authabort;
         }
     } else {
-        vs->sasl.wantSSF = 1;
+        vs->sasl.wantSSF = !vnc_socket_is_unix(vs->sioc);
     }
 
     memset (&secprops, 0, sizeof secprops);