Disable putting filter block to block cache

Summary: This bug caused server crash issues because the filter block is too big and kept purging out of cache.

Test Plan: Wrote a new unit tests to make sure it works.

Reviewers: dhruba, haobo, igor, sdong

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D16221

table/block_based_table_reader.h

@@ -90,6 +90,9 @@ class BlockBasedTable : public TableReader {
 
   ~BlockBasedTable();
 
+  bool TEST_filter_block_preloaded() const;
+  bool TEST_index_block_preloaded() const;
+
  private:
   template <class TValue>
   struct CachableEntry;