Don't do case lookups when we have the right case already.

This is a missed part of the original "[Bleeding] Use case from player data
for OfflinePlayer. Fixes BUKKIT-519" commit. It avoids doing (somewhat
expensive) lookups of player data to find the correct capitalization inside
getOfflinePlayers() as we're already loading their name from the player data
and thus have the correct capitalization.

src/main/java/org/bukkit/craftbukkit/CraftServer.java

@@ -1178,7 +1178,7 @@ public final class CraftServer implements Server {
         Set<OfflinePlayer> players = new HashSet<OfflinePlayer>();
 
         for (String file : files) {
-            players.add(getOfflinePlayer(file.substring(0, file.length() - 4)));
+            players.add(getOfflinePlayer(file.substring(0, file.length() - 4), false));
         }
         players.addAll(Arrays.asList(getOnlinePlayers()));