a4f772efa7
If we add a new hook, not at the end, while hooks are getting called, then iteration could be messed up (e.g. calling a plugin twice, or skipping one). The simplest thing is to defer updates until nobody is calling the hook. In theory this could livelock, in practice it won't. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>