Plug possible calls into ip6?_output() without network epoch from SCTP
bluntly adding epoch entrance into the macro that SCTP uses to call
ip6?_output(). This definitely will introduce several epoch recursions.

Reported by: https://syzkaller.appspot.com/bug?id=79f03f574594a5be464997310896765c458ed80a
Reported by: https://syzkaller.appspot.com/bug?id=07c6f52106cddbe356cc2b2f3664a1c51cc0dadf