Stop start-delay-timer instead of auto-start-timer on empty lobby.

Due to the start-delay-timer holding a reference to the
auto-start-timer as its internal callback, the start-delay-timer
should be stopped, when both timers should be stopped.

resources/plugin.yml

@@ -1,7 +1,7 @@
 name: MobArena
 author: garbagemule
 main: com.garbagemule.MobArena.MobArena
-version: 0.96.3.3
+version: 0.96.3.4
 softdepend: [Multiverse-Core,Towny,Heroes,MagicSpells,Vault]
 commands:
     ma: