clatd: fix endianness of multicast drop This is a *critical* fix for http://go/aog/3514294 'Drop egress multicast on clat interface' Bug: 404457155 Test: TreeHugger Signed-off-by: Maciej Żenczykowski <[email protected]> Change-Id: If14ef730f78c7e991842a678260dd20df607b1ec