udev: wake up the udev thread for stopping it

Signal the udev thread the change of `priv->threadQuit` by using the
thread condition.

Signed-off-by: Marc Hartmayer <mhartmay@linux.ibm.com>
Reviewed-by: John Ferlan <jferlan@redhat.com>

src/node_device/node_device_udev.c

@@ -1805,6 +1805,7 @@ nodeStateInitializeEnumerate(void *opaque)
     ignore_value(virEventRemoveHandle(priv->watch));
     priv->watch = -1;
     priv->threadQuit = true;
+    virCondSignal(&priv->threadCond);
     virObjectUnlock(priv);
 }