Respect silent nick change in mucs

Profanity would ignore the silent nick change in some places. The roster
and history would show the correct nick, new messages from the current
user and the "Autojoined <jid> as <nick>" message would show the wrong
one. This commit fixes that problem.

Fixes https://github.com/profanity-im/profanity/issues/757

src/xmpp/presence.c

@@ -752,6 +752,8 @@ _muc_user_self_handler(xmpp_stanza_t* stanza)
             log_warning("presence: jid without resource");
             return;
         }
+
+        muc_nick_change_complete(room, nick);
         char* reason = stanza_get_reason(stanza);
         char* show_str = stanza_get_show(stanza, "online");
         char* status_str = stanza_get_status(stanza, NULL);