Do not change the nick when joining a second room with a different nick

As the doc says, the nick changes must be explicit in an already joined
room, and not when joining a room.

tests/end_to_end/__main__.py

@@ -798,6 +798,33 @@ if __name__ == '__main__':
                          ("/message[@from='{lower_nick_two}%{irc_server_one}'][@to='{jid_one}/{resource_one}'][@type='chat']/body[text()='second']",),
                          ]),
                  ]),
+        Scenario("channel_join_with_different_nick",
+                 [
+                     handshake_sequence(),
+                     partial(send_stanza,
+                             "<presence from='{jid_one}/{resource_one}' to='#foo%{irc_server_one}/{nick_one}' />"),
+                     connection_sequence("irc.localhost", '{jid_one}/{resource_one}'),
+                     partial(expect_stanza,
+                             "/message/body[text()='Mode #foo [+nt] by {irc_host_one}']"),
+                     partial(expect_stanza,
+                             ("/presence[@to='{jid_one}/{resource_one}'][@from='#foo%{irc_server_one}/{nick_one}']/muc_user:x/muc_user:item[@affiliation='admin'][@role='moderator']",
+                              "/presence/muc_user:x/muc_user:status[@code='110']")
+                             ),
+                     partial(expect_stanza, "/message[@from='#foo%{irc_server_one}'][@type='groupchat'][@to='{jid_one}/{resource_one}']/subject[not(text())]"),
+
+                     # The same resource joins a different channel with a different nick
+                     partial(send_stanza,
+                             "<presence from='{jid_one}/{resource_one}' to='#bar%{irc_server_one}/{nick_two}' />"),
+
+                     # We must receive a join presence in response, without any nick change (nick_two) must be ignored
+                     partial(expect_stanza,
+                             "/message/body[text()='Mode #bar [+nt] by {irc_host_one}']"),
+                     partial(expect_stanza,
+                             ("/presence[@to='{jid_one}/{resource_one}'][@from='#bar%{irc_server_one}/{nick_one}']/muc_user:x/muc_user:item[@affiliation='admin'][@role='moderator']",
+                              "/presence/muc_user:x/muc_user:status[@code='110']")
+                             ),
+                     partial(expect_stanza, "/message[@from='#bar%{irc_server_one}'][@type='groupchat'][@to='{jid_one}/{resource_one}']/subject[not(text())]"),
+                 ]),
         Scenario("channel_messages",
                  [
                      handshake_sequence(),