unit can survive after death in "share until death" by loading unit in a transport that have been given

player A give a transport to player B,
B load unit into the transport,
if B die, then A get the transport back + the unit in it.

/!\ it's a way to give unit alive when they should die /!\

was mentioned in #526 but never been addressed.

reproduced her : http://content.faforever.com/faf/vault/replay_vault/replay.php?id=7048300
logs : https://gist.github.com/shalkya/fb04787341aac7e03b392819cacf6b49