hw/xen: do not use aio_set_fd_handler(is_external=true) in xen_xenstore

There is no need to suspend activity between aio_disable_external() and
aio_enable_external(), which is mainly used for the block layer's drain
operation.

This is part of ongoing work to remove the aio_disable_external() API.

Reviewed-by: David Woodhouse <dwmw@amazon.co.uk>
Reviewed-by: Paul Durrant <paul@xen.org>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20230516190238.8401-9-stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

hw/i386/kvm/xen_xenstore.c

@@ -133,7 +133,7 @@ static void xen_xenstore_realize(DeviceState *dev, Error **errp)
         error_setg(errp, "Xenstore evtchn port init failed");
         return;
     }
-    aio_set_fd_handler(qemu_get_aio_context(), xen_be_evtchn_fd(s->eh), true,
+    aio_set_fd_handler(qemu_get_aio_context(), xen_be_evtchn_fd(s->eh), false,
                        xen_xenstore_event, NULL, NULL, NULL, s);
 
     s->impl = xs_impl_create(xen_domid);