OF-2042: MUC order of events: wait for presence broadcast
This commit builds on the earlier commit, to ensure that the order-of-events as defined in the MUC XEP is observed. Notably, Openfire should wait (up to a configurable amount of time) until initial presence broadcast has been completed, before sending room history and subject.
OF-2049: Do not remove room before presences are sent
This commit aims to make subsequent actions wait on the completion of others. This should prevent the room from being deleted before the unavailable presence stanzas have been sent (which otherwise causes issues, as the room is used to compose those stanzas).
