mod_authz_delegate: make resistant against startup order issues There is no guarantee that the target_host gets activated and initialized before the host this module is loaded on. As add_default_permission is called during load time by many modules, we need to be prepared to queue stuff.

This module blocks configured queries that change server state.

E.g. to make vCard storage read-only:

``` lua
readonly_stores = {
	vcard = { "vcard-temp", "vCard" };
}
```