Fix compile failure on Travis
Fix compile failure on Travis

Summary:
Travis is complaining against using {} to initialize KVMap: https://travis-ci.org/facebook/rocksdb/jobs/84132600

      db/compaction_job_test.cc:526:26: error: chosen constructor is explicit in copy-initialization
        RunCompaction({files}, {});

This diff should fix it

Test Plan: travis

Reviewers: sdong

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D48309

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