gajim is not seen as muc compliant when there is a nickname conflict

[misc]

If I connect twice in a room with the same nickname, most muc implementation will send a error for nickname conflict. So gajim ask me to choose another nickname.

Once I have choosed this, the presence packet sent is lacking a x element with http://jabber.org/protocol/muc namespace.

<presence to="jabberfr@chat.jabberfr.org/Misc" id="40">
<x xmlns="vcard-temp:x:update">
<photo>5ab17f67d5a57e280835448cd854b84eb4a231bd</photo>
</x>
<c xmlns="http://jabber.org/protocol/caps" node="http://gajim.org/caps" ext="ftrans xhtml" ver="0.11.0.1" />
</presence>

One side effect of the missing element is that muconf is sending useless message, as if we were a gc 1.0 client ( like plain message saying "foo has left" ).

After looking at the code, it seems that first presence packet is sent by join_gc, in source:src/common/connection.py, but the secund, with the new nick, is sent by "change_gc_nick", in source:src/common/connection.py, and change_gc_nick do not add the x element.

Here is a patch, I am not sure however that this is logical. I think using change_gc_nick for new presence is some kind of abuse of the function.

[misc]

patch to send the proper x element if we change nick and not in a room

[jim++]

(In [7964]) Delete change_nick() func, use join_gc() instead. Fixes #2903.

[Jim++]

Better this way, thanks for investigate on that Misc.