avoid collision with master branch in check format
avoid collision with master branch in check format

Summary:
The new local branch specified with -b cannot be called master. Use tmp prefix to avoid name collision.
Closes https://github.com/facebook/rocksdb/pull/2600

Differential Revision: D5442944

Pulled By: maysamyabandeh

fbshipit-source-id: 4a623d9b21d6cc01bee812b2799790315bdf5f6e

Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,SunguckLee/RocksDB,Andymic/rocksdb,Andymic/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,Andymic/rocksdb,Andymic/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,SunguckLee/RocksDB,bbiao/rocksdb,Andymic/rocksdb,SunguckLee/RocksDB