Comment 2 for bug 1575225

Upon closer examination, the present behavior is correct since ICMPV6_ALLOWED_TYPES controls the ingress ICMPV6 types, and instances send MLDv2 reports in response to MLD queries. ICMPV6_ALLOWED_TYPES does not need to be updated for MLDv2, and https://review.openstack.org/#/c/300233/ now correctly permits egress of MLDv2 reports.