Update preRemove middleware in check model.
Update preRemove middleware in check model.

This fixes the deletion of related stats upon check deletion.

jraigneau/watchdog,rkmallik/uptime-openshift,RafeHatfield/nodeuptime,cloudfoundry-community/uptime-cfready,phanan/uptime,blendlabs/uptime,prune998/uptime,bathree/uptime,aregpetrosyan/web,fzaninotto/uptime,traskat/uptime,heamon7/uptime,memezilla/uptime,ptisp/uptime,gleicon/uptime,scalp42/uptime,sinkingshriek/uptime,nerevu/uptime,WillGuan105/uptime,Maluuba/uptime,MichaelStephan/uptime,ifavo/uptime,blackboard/uptime,brianjking/uptime,rkmallik/uptime-openshift,SpringerPE/uptime,GuptaVineet-IBM/upTime_ford,aregpetrosyan/web,arthurpro/uptime,ptisp/uptime,0x8BADFOOD/uptime,f33rx/docker-uptime,nacyot/uptime,SaravananPerumal23/uptime2,erpframework/uptime,nerevu/uptime,b-pedzik/uptime,SufianHassan/uptime,askcs/uptime,f33rx/docker-uptime,SaravananPerumal23/uptime2