canceling nickname change break various stuff
Step to reproduce :
- enter a muc room, with more than one person
- try to change your nickname for one that is already taken
- when the dialog telling you to use a different nickname appear, just hit cancel
- try to change your presence
Expected result : no error message appear
Observed result : a message apear, and the xml sent by gajim is wrong
It seems gajim change the internal structure ( ie self.nick ) before the muc component send back the presence to ack the change, thuis leading to various problem. Here is a proposed patch, that place the new nick in a temporary member and that copy it once we have received a presence stanza.