This conditional must also check if the cached datagram's age is < Tactive before including it in the sequence list.

Note to self: This is likely as simple as replacing the if block with something like:
```
if(MCAST_PACKET_IS_USED(locmpptr) &&
  (locmpptr->active < TRICKLE_ACTIVE(&t[(sl->flags & SEQUENCE_LIST_M_BIT) != 0]))) {
```