Rework hack for synchronous event processing to make it reliable.
    
    Previously a pointer to event was used as unique ID which was a terrible
    idea. The address was sometimes reused by allocator. Address re-use
    lead to false positives in event tracing logic and thus some events
    were processed asynchronously even if synchronous processing was requested.
    
    https://fedorahosted.org/bind-dyndb-ldap/ticket/125