Fixed a bug in RocksDB Statistics where flush is considered as compaction

Summary: Fixed a bug in RocksDB Statistics where flush is considered as compaction

Test Plan: unit test

Reviewers: sdong, IslamAbdelRahman, rven, kradhakrishnan, andrewkr

Reviewed By: andrewkr

Subscribers: andrewkr, dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D56271

db/flush_job.cc

@@ -300,7 +300,7 @@ Status FlushJob::WriteLevel0Table(const autovector<MemTable*>& mems,
   cfd_->internal_stats()->AddCompactionStats(0 /* level */, stats);
   cfd_->internal_stats()->AddCFStats(InternalStats::BYTES_FLUSHED,
                                      meta->fd.GetFileSize());
-  RecordTick(stats_, COMPACT_WRITE_BYTES, meta->fd.GetFileSize());
+  RecordTick(stats_, FLUSH_WRITE_BYTES, meta->fd.GetFileSize());
   return s;
 }