CLI option & Rename() allow overwrite
CLI option & Rename() allow overwrite

Summary: this test support CLI option to select HdfsEnv/NativeHdfsEnv now. The latter one is default. add test about when Rename(src, target) should overwrite target

Test Plan: existing test

Reviewers: sdong, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D60399

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