remove TailingIterator reference in db_impl.h
remove TailingIterator reference in db_impl.h

Summary: as title

Test Plan: make release

Reviewers: igor

Differential Revision: https://reviews.facebook.net/D23073

luckywhu/rocksdb,zhangpng/rocksdb,mbarbon/rocksdb,ylong/rocksdb,mbarbon/rocksdb,JoeWoo/rocksdb,geraldoandradee/rocksdb,SunguckLee/RocksDB,biddyweb/rocksdb,tizzybec/rocksdb,temicai/rocksdb,flabby/rocksdb,Applied-Duality/rocksdb,OverlordQ/rocksdb,Vaisman/rocksdb,facebook/rocksdb,Vaisman/rocksdb,wat-ze-hex/rocksdb,norton/rocksdb,siddhartharay007/rocksdb,siddhartharay007/rocksdb,dkorolev/rocksdb,RyanTech/rocksdb,virtdb/rocksdb,biddyweb/rocksdb,caijieming-baidu/rocksdb,geraldoandradee/rocksdb,Andymic/rocksdb,amyvmiwei/rocksdb,wskplho/rocksdb,IMCG/RcoksDB,rDSN-Projects/rocksdb.replicated,temicai/rocksdb,makelivedotnet/rocksdb,rDSN-Projects/rocksdb.replicated,IMCG/RcoksDB,JohnPJenkins/rocksdb,dkorolev/rocksdb,JackLian/rocksdb,JoeWoo/rocksdb,Vaisman/rocksdb,luckywhu/rocksdb,biddyweb/rocksdb,anagav/rocksdb,vashstorm/rocksdb,ryneli/rocksdb,fengshao0907/rocksdb,Applied-Duality/rocksdb,vmx/rocksdb,Vaisman/rocksdb,geraldoandradee/rocksdb,ylong/rocksdb,ryneli/rocksdb,wlqGit/rocksdb,tsheasha/rocksdb,facebook/rocksdb,fengshao0907/rocksdb,alihalabyah/rocksdb,vmx/rocksdb,bbiao/rocksdb,wenduo/rocksdb,jalexanderqed/rocksdb,geraldoandradee/rocksdb,JackLian/rocksdb,skunkwerks/rocksdb,tizzybec/rocksdb,wlqGit/rocksdb,Applied-Duality/rocksdb,anagav/rocksdb,wat-ze-hex/rocksdb,Vaisman/rocksdb,kaschaeffer/rocksdb,flabby/rocksdb,amyvmiwei/rocksdb,Andymic/rocksdb,dkorolev/rocksdb,tsheasha/rocksdb,vashstorm/rocksdb,JoeWoo/rocksdb,NickCis/rocksdb,ryneli/rocksdb,JoeWoo/rocksdb,ryneli/rocksdb,IMCG/RcoksDB,makelivedotnet/rocksdb,OverlordQ/rocksdb,mbarbon/rocksdb,wat-ze-hex/rocksdb,facebook/rocksdb,temicai/rocksdb,bbiao/rocksdb,RyanTech/rocksdb,wat-ze-hex/rocksdb,norton/rocksdb,dkorolev/rocksdb,ryneli/rocksdb,luckywhu/rocksdb,caijieming-baidu/rocksdb,lgscofield/rocksdb,OverlordQ/rocksdb,wenduo/rocksdb,wenduo/rocksdb,biddyweb/rocksdb,fengshao0907/rocksdb,tsheasha/rocksdb,hobinyoon/rocksdb,skunkwerks/rocksdb,lgscofield/rocksdb,lgscofield/rocksdb,biddyweb/rocksdb,wat-ze-hex/rocksdb,Andymic/rocksdb,ylong/rocksdb,lgscofield/rocksdb,temicai/rocksdb,wenduo/rocksdb,amyvmiwei/rocksdb,caijieming-baidu/rocksdb,JoeWoo/rocksdb,Applied-Duality/rocksdb,zhangpng/rocksdb,virtdb/rocksdb,wskplho/rocksdb,rDSN-Projects/rocksdb.replicated,wenduo/rocksdb,zhangpng/rocksdb,SunguckLee/RocksDB,siddhartharay007/rocksdb,JackLian/rocksdb,hobinyoon/rocksdb,RyanTech/rocksdb,RyanTech/rocksdb,mbarbon/rocksdb,rDSN-Projects/rocksdb.replicated,dkorolev/rocksdb,temicai/rocksdb,norton/rocksdb,geraldoandradee/rocksdb,NickCis/rocksdb,flabby/rocksdb,tsheasha/rocksdb,biddyweb/rocksdb,vashstorm/rocksdb,RyanTech/rocksdb,kaschaeffer/rocksdb,geraldoandradee/rocksdb,virtdb/rocksdb,tsheasha/rocksdb,IMCG/RcoksDB,siddhartharay007/rocksdb,makelivedotnet/rocksdb,OverlordQ/rocksdb,Andymic/rocksdb,amyvmiwei/rocksdb,wat-ze-hex/rocksdb,kaschaeffer/rocksdb,ylong/rocksdb,Applied-Duality/rocksdb,wskplho/rocksdb,vmx/rocksdb,skunkwerks/rocksdb,JohnPJenkins/rocksdb,JohnPJenkins/rocksdb,zhangpng/rocksdb,facebook/rocksdb,sorphi/rocksdb,geraldoandradee/rocksdb,caijieming-baidu/rocksdb,tizzybec/rocksdb,NickCis/rocksdb,bbiao/rocksdb,tizzybec/rocksdb,hobinyoon/rocksdb,wlqGit/rocksdb,ylong/rocksdb,JohnPJenkins/rocksdb,jalexanderqed/rocksdb,sorphi/rocksdb,jalexanderqed/rocksdb,ryneli/rocksdb,RyanTech/rocksdb,skunkwerks/rocksdb,kaschaeffer/rocksdb,SunguckLee/RocksDB,wat-ze-hex/rocksdb,zhangpng/rocksdb,luckywhu/rocksdb,bbiao/rocksdb,Vaisman/rocksdb,Andymic/rocksdb,anagav/rocksdb,alihalabyah/rocksdb,vmx/rocksdb,JackLian/rocksdb,rDSN-Projects/rocksdb.replicated,fengshao0907/rocksdb,facebook/rocksdb,tsheasha/rocksdb,kaschaeffer/rocksdb,jalexanderqed/rocksdb,NickCis/rocksdb,wat-ze-hex/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,wenduo/rocksdb,makelivedotnet/rocksdb,luckywhu/rocksdb,vashstorm/rocksdb,makelivedotnet/rocksdb,flabby/rocksdb,SunguckLee/RocksDB,dkorolev/rocksdb,virtdb/rocksdb,IMCG/RcoksDB,wlqGit/rocksdb,sorphi/rocksdb,sorphi/rocksdb,NickCis/rocksdb,JohnPJenkins/rocksdb,JohnPJenkins/rocksdb,facebook/rocksdb,flabby/rocksdb,biddyweb/rocksdb,Andymic/rocksdb,siddhartharay007/rocksdb,siddhartharay007/rocksdb,JohnPJenkins/rocksdb,skunkwerks/rocksdb,JoeWoo/rocksdb,lgscofield/rocksdb,sorphi/rocksdb,vmx/rocksdb,ryneli/rocksdb,temicai/rocksdb,sorphi/rocksdb,OverlordQ/rocksdb,vashstorm/rocksdb,skunkwerks/rocksdb,anagav/rocksdb,skunkwerks/rocksdb,temicai/rocksdb,vashstorm/rocksdb,bbiao/rocksdb,facebook/rocksdb,Applied-Duality/rocksdb,fengshao0907/rocksdb,alihalabyah/rocksdb,virtdb/rocksdb,bbiao/rocksdb,wlqGit/rocksdb,SunguckLee/RocksDB,anagav/rocksdb,lgscofield/rocksdb,luckywhu/rocksdb,tizzybec/rocksdb,virtdb/rocksdb,ylong/rocksdb,RyanTech/rocksdb,JoeWoo/rocksdb,tsheasha/rocksdb,makelivedotnet/rocksdb,NickCis/rocksdb,wenduo/rocksdb,NickCis/rocksdb,norton/rocksdb,luckywhu/rocksdb,virtdb/rocksdb,caijieming-baidu/rocksdb,IMCG/RcoksDB,Vaisman/rocksdb,facebook/rocksdb,Andymic/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb,norton/rocksdb,tizzybec/rocksdb,wskplho/rocksdb,wlqGit/rocksdb,bbiao/rocksdb,amyvmiwei/rocksdb,wenduo/rocksdb,JackLian/rocksdb,IMCG/RcoksDB,hobinyoon/rocksdb,zhangpng/rocksdb,tizzybec/rocksdb,mbarbon/rocksdb,kaschaeffer/rocksdb,caijieming-baidu/rocksdb,flabby/rocksdb,rDSN-Projects/rocksdb.replicated,OverlordQ/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,wskplho/rocksdb,rDSN-Projects/rocksdb.replicated,alihalabyah/rocksdb,vmx/rocksdb,kaschaeffer/rocksdb,tsheasha/rocksdb,alihalabyah/rocksdb,vmx/rocksdb,mbarbon/rocksdb,flabby/rocksdb,amyvmiwei/rocksdb,bbiao/rocksdb,vashstorm/rocksdb,fengshao0907/rocksdb,zhangpng/rocksdb,norton/rocksdb,vmx/rocksdb,mbarbon/rocksdb,wskplho/rocksdb,JackLian/rocksdb,amyvmiwei/rocksdb,sorphi/rocksdb,caijieming-baidu/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,alihalabyah/rocksdb,hobinyoon/rocksdb,dkorolev/rocksdb,norton/rocksdb,jalexanderqed/rocksdb,lgscofield/rocksdb,alihalabyah/rocksdb,fengshao0907/rocksdb,Applied-Duality/rocksdb,wskplho/rocksdb,ylong/rocksdb,norton/rocksdb,anagav/rocksdb,makelivedotnet/rocksdb,JackLian/rocksdb,siddhartharay007/rocksdb,OverlordQ/rocksdb,wlqGit/rocksdb,SunguckLee/RocksDB,anagav/rocksdb