Always filter out multicast from reflection

Instances will try IPv6 neighbour discovery via multicast
even in an IPv4-only cloud and can throw errors
if they see inbound packets from their own MAC address

Closes-bug: #1229625
Closes-rally-bug: DE711

Change-Id: I3539e788fe07519d87ce7c3800c5d38b7bd99d3b
(cherry picked from commit 9c044d2c94812e18cf84927fbf719cd073fe6c4f)