prediction: bug fix in ValidationChecker; minor code refactor
prediction: bug fix in ValidationChecker; minor code refactor

wanglei828/apollo,jinghaomiao/apollo,ApolloAuto/apollo,xiaoxq/apollo,ApolloAuto/apollo,jinghaomiao/apollo,ApolloAuto/apollo,wanglei828/apollo,ycool/apollo,ycool/apollo,ycool/apollo,ApolloAuto/apollo,wanglei828/apollo,xiaoxq/apollo,ycool/apollo,xiaoxq/apollo,ycool/apollo,ApolloAuto/apollo,wanglei828/apollo,xiaoxq/apollo,xiaoxq/apollo,ApolloAuto/apollo,jinghaomiao/apollo,wanglei828/apollo,xiaoxq/apollo,jinghaomiao/apollo,jinghaomiao/apollo,jinghaomiao/apollo,wanglei828/apollo,ycool/apollo