telepathy-gabble: man-in-the-middle attack

Maksim Otstavnov discovered that the Wocky submodule used by telepathy-gabble, the Jabber/XMPP connection manager for the Telepathy framework, does not respect the tls-required flag on legacy Jabber servers. A network intermediary could use this vulnerability to bypass TLS verification and perform a man-in-the-middle attack.