Initialize threads later in constructor
Initialize threads later in constructor

Summary: This addresses a test failure where an exception occured in the constructor's call to CreateDirIfMissing(). The existence of unjoined threads prevented this exception from propogating properly. See http://stackoverflow.com/questions/7381757/c-terminate-called-without-an-active-exception

Test Plan: Re-run tests from task #7626266

Reviewers: sdong, anthony, igor

Reviewed By: igor

Subscribers: dhruba

Differential Revision: https://reviews.facebook.net/D41313

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