e2e: Implicitely include the handshake in all tests

Instead of having to write it manually everytime

tests/end_to_end/scenarios/encoded_channel_join.py

@@ -1,7 +1,6 @@
 from scenarios import *
 
 scenario = (
-    sequences.handshake(),
     send_stanza("<presence from='{jid_one}/{resource_one}' to='#biboumi\\40louiz.org\\3a80%{irc_server_one}/{nick_one}' />"),
     sequences.connection("irc.localhost", '{jid_one}/{resource_one}'),
     expect_stanza("/message/body[text()='Mode #biboumi@louiz.org:80 [+nt] by {irc_host_one}']"),