rm -rf in make clean
rm -rf in make clean

Summary: Without this I get bunch of questions when I run `make clean`

Test Plan: no more questions!

Reviewers: rven, yhchiang, meyering, anthony

Reviewed By: meyering, anthony

Subscribers: meyering, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D38145

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