Fix bug in leaveBattle
Fix bug in leaveBattle

It would show the other side as left, instead of your side.

Zarel/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,panpawn/Gold-Client,submindraikou/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,submindraikou/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,QuiteQuiet/Pokemon-Showdown-Client,Zarel/Pokemon-Showdown-Client,panpawn/Gold-Client,Zarel/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,asgdf/Pokemon-Showdown-Client,sirDonovan/Pokemon-Showdown-Client,panpawn/Gold-Client