Fix incompabilities with per-world inventories.

War saved a player's state before they were teleported into the warzone.
This causes issues if the lobby is in another world and the server is
using plugins to manage per-world inventories. Essentially, the player is
getting their inventory from world A saved, teleported to warzone in world
B, their state being restored in B, then teleported to A. Per-world
inventory plugins save and restore inventories on every
cross-world-teleport. This causes blank inventories when a player joins a
warzone and the player gets the items from the zone when they leave.

This issue is easily fixed by teleporting players to the warzone's world
before saving their state. This is merely a standardization of state
save/restore order.
Fixes gh-533

Prevents players from teleporting or moving out of a warzone in play.