commit 4a7f5e2c4c1 breaks improxy

I have some troubles with this commit.

I tested improxy five months ago and reverted this commit because I don't need to forward packets from one downstream to other interfaces. After that my router started to forward IPv6 multicast from wan to lan correctly.

I decided to check it again.
In this commit you disabled k_mcast_msfilter.
As a result, Linux Kernel sends MLD2 reports (leaves) with incorect record type.
Attachment contains additional information:

2018-07-02 13:06:00.058 INFO(wan): Expecting MLDv2 record type CHANGE_TO_INCLUDE_MODE for group ff0e::1, but found CHANGE_TO_EXCLUDE_MODE