x/net/ipv6: TestIPPerInterfaceSinglePacketConnWithSingleGroupListener broken on freebsd-386 for Go 1.11

[bradfitz]

TestIPPerInterfaceSinglePacketConnWithSingleGroupListener is broken on freebsd-386-* with Go 1.11:

https://build.golang.org/log/7c758c236a9eff9b87a8fc6adb6013af786c2eb7

--- FAIL: TestIPPerInterfaceSinglePacketConnWithSingleGroupListener (0.00s)
    multicastlistener_test.go:247: listen ip6:ipv6-icmp 0:fe:8000::%lo0: bind: can't assign requested address
FAIL
FAIL	golang.org/x/net/ipv6	0.019s

@mikioh, can you fix?

[mikioh]

Dupe of #28826. Please backport the CLs to release-branch.go1.11 if necessary; I cannot make backport CLs.

PS: freebsd-386 builders are actually freebsd-compat32 builders.

[mikioh]

Please backport the CLs

CL 139577 and CL 139917.

[bradfitz]

Re-opening the bug, as this isn't fix. The build.golang.org dashboard is still red.

[gopherbot]

Change https://golang.org/cl/170617 mentions this issue: [release-branch.go1.11] route: re-adjust routing message alignment for FreeBSD 386 emulation

[gopherbot]

Change https://golang.org/cl/170618 mentions this issue: [release-branch.go1.11] route: don't run NET_RT_IFLIST vs. NET_RT_IFLISTL test in 386 emulation (again)