Broadcast original 'unavailable' presence when leaving the room.
When a client sends a presence 'unavailable' stanza to leave a multi-user chat room, Openfire broadcasts not that stanza, but one that was received earlier (and is modified to include 'unavailable').
This appears to be an oversight, combined with a better-safe-than-sorry override of the presence type.
Openfire should broadcast the original stanza (modified to add some metadata where needed). This will, for instance, keep intact the reflected stanza ID.