io: remove mistaken call to object_ref on QTask

The QTask struct is just a standalone struct, not a QOM Object,
so calling object_ref() on it is not appropriate. This results
in mangling the 'destroy' field in the QTask struct, causing
the later call to qtask_free() to try to call the function
at address 0x1, with predictably segfault happy results.

There is in fact no need for ref counting with QTask, as the
call to qtask_abort() or qtask_complete() will automatically
free associated memory.

This fixes the crash shown in

  https://bugs.launchpad.net/qemu/+bug/1589923

Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
(cherry picked from commit bc35d51077)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

io/channel-websock.c

@@ -316,14 +316,13 @@ static gboolean qio_channel_websock_handshake_io(QIOChannel *ioc,
         return TRUE;
     }
 
-    object_ref(OBJECT(task));
     trace_qio_channel_websock_handshake_reply(ioc);
     qio_channel_add_watch(
         wioc->master,
         G_IO_OUT,
         qio_channel_websock_handshake_send,
         task,
-        (GDestroyNotify)object_unref);
+        NULL);
     return FALSE;
 }