Fix wrong exception being thrown on invalid instance types passed to 'executor'.
Fix wrong exception being thrown on invalid instance types passed to 'executor'.

lvbaosong/predis,oswaldderiemaecker/predis,mrkeng/predis,johnhelmuth/predis,CloudSide/predis,moria/predis,gencer/predis,stokes3452/predis,vend/predis,quangnguyen90/predis,WalterShe/predis,nrk/predis,gopalindians/predis,dominics/predis,protomouse/predis,zhangyancoder/predis,RudyJessop/predis,channelgrabber/predis,SwelenFrance/predis,dzung2t/predis,nguyenthaihan/predis,RedisLabs/predis,SecureCloud-biz/predis