Revert "Exempt multicast addresses from five-second neighbor lifetime"

This reverts commit e5fe052c as it
breaks some ABIs that people are relying on.

The need for this in an android device seems low at this point in time.
If it is deemed that this is needed, this patch can be revisited and
added back in a different way to not touch the abi.

Bug: 161946584
Signed-off-by: Greg Kroah-Hartman <gregkh@google.com>
Change-Id: I019a290c6d7d54d50a143a93063bcd88d80d6c98