fixed up some ending event emissions

Not just pushing because it may be "controversial"... This was done in an attempt to make things more consistent. Now:
- 'canceled' only fires for the UAS receiving the CANCEL
- 'rejected' only fires for the UAC being rejected (and not after a cancel, yes this did happen BUT not every time).
- 'failed' always fires before a call is initiated.
- 'bye' is only emitted by the person who is receiving the BYE

Although this pull request may not be accepted, something along these lines needs to be done to make these emissions more consistent.