With how fast UML is hostapd events were being sent out prior to
ever calling wait_for_event. Instead set an IO watch on the control
socket and cache all events as they come. Then, when wait_for_event
is called, it can reference this list. If the event is found any
older events are purged from the list.
The AP-ENABLED event needed a special case because hostapd gets
started before the IO watch can be registered. To fix this an
enabled property was added which queries the state directly. This
is checked first, and if not enabled wait_for_event continues normally.
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