e2e: Implicitely include the handshake in all tests

Instead of having to write it manually everytime

tests/end_to_end/scenarios/irc_server_connection_failure.py

@@ -1,7 +1,6 @@
 from scenarios import *
 
 scenario = (
-    sequences.handshake(),
     send_stanza("<presence from='{jid_one}/{resource_one}' to='#foo%doesnotexist@{biboumi_host}/{nick_one}' />"),
     expect_stanza("/message/body[text()='Connecting to doesnotexist:6697 (encrypted)']"),
     expect_stanza("/message/body[re:test(text(), 'Connection failed: (Domain name not found|Name or service not known)')]"),