fix test failure
fix test failure

Summary: fix Rocksdb Unit Test USER_FAILURE

Test Plan: make all check -j64

Reviewers: sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D60603

vmx/rocksdb,facebook/rocksdb,vmx/rocksdb,vmx/rocksdb,ryneli/rocksdb,bbiao/rocksdb,hobinyoon/rocksdb,SunguckLee/RocksDB,ryneli/rocksdb,OverlordQ/rocksdb,Andymic/rocksdb,Andymic/rocksdb,wenduo/rocksdb,hobinyoon/rocksdb,facebook/rocksdb,vmx/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,vmx/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,jalexanderqed/rocksdb,tsheasha/rocksdb,tsheasha/rocksdb,SunguckLee/RocksDB,norton/rocksdb,hobinyoon/rocksdb,tsheasha/rocksdb,ryneli/rocksdb,facebook/rocksdb,bbiao/rocksdb,vmx/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,ryneli/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb,hobinyoon/rocksdb,hobinyoon/rocksdb,jalexanderqed/rocksdb,wat-ze-hex/rocksdb,facebook/rocksdb,norton/rocksdb,wat-ze-hex/rocksdb,Andymic/rocksdb,bbiao/rocksdb,wenduo/rocksdb,bbiao/rocksdb,wat-ze-hex/rocksdb,wenduo/rocksdb,jalexanderqed/rocksdb,OverlordQ/rocksdb,wat-ze-hex/rocksdb,norton/rocksdb,norton/rocksdb,Andymic/rocksdb,tsheasha/rocksdb,SunguckLee/RocksDB,norton/rocksdb,jalexanderqed/rocksdb,wenduo/rocksdb,wenduo/rocksdb,wat-ze-hex/rocksdb,jalexanderqed/rocksdb,Andymic/rocksdb,facebook/rocksdb,norton/rocksdb,bbiao/rocksdb,wat-ze-hex/rocksdb,ryneli/rocksdb,tsheasha/rocksdb,SunguckLee/RocksDB,hobinyoon/rocksdb,facebook/rocksdb,facebook/rocksdb,wenduo/rocksdb,OverlordQ/rocksdb,bbiao/rocksdb,facebook/rocksdb,vmx/rocksdb,OverlordQ/rocksdb,wat-ze-hex/rocksdb,ryneli/rocksdb,vmx/rocksdb,wat-ze-hex/rocksdb,Andymic/rocksdb,wenduo/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,OverlordQ/rocksdb,norton/rocksdb,tsheasha/rocksdb,hobinyoon/rocksdb,ryneli/rocksdb,norton/rocksdb,Andymic/rocksdb,tsheasha/rocksdb,tsheasha/rocksdb,OverlordQ/rocksdb,OverlordQ/rocksdb