Fix everyone receiving the same type of item

[Seeloewen]

Currently, while everyone receives a random item when playing multiplayer, they always get the same type. If a normal item is rolled, everyone gets a random normal item at the same time. When a goat horn is rolled, a everyone receives a random goat horn.
It should theoretically be possible to make everyone receive a random type of item. By rolling the random number for each person seperately and not for the RandomItemGiver in general, everyone gets a random item from a random loot table.