Break down PinnedDataIteratorRandomized
Break down PinnedDataIteratorRandomized

Summary:
Its timing out under tsan.
Closes https://github.com/facebook/rocksdb/pull/2928

Differential Revision: D5911766

Pulled By: maysamyabandeh

fbshipit-source-id: 2faacc07752ac8713a3a2abb5a4c4b7ae3bdf208

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