Check starts_with(prefix) in MultiPrefixIterate
Check starts_with(prefix) in MultiPrefixIterate

Summary: We switched to prefix_seek method of seeking. This means that anytime we check Valid(), we also need to check starts_with(prefix)

Test Plan: ran db_stress

Reviewers: ljin

Reviewed By: ljin

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16953

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