When Options.max_num_files=-1, non level0 files also by pass table cache

Summary:
This is the part that was not finished when doing the Options.max_num_files=-1 feature. For iterating non level0 SST files (which was done using two level iterator), table cache is not bypassed. With this patch, the leftover feature is done.

Test Plan: make all check; change Options.max_num_files=-1 in one of the tests to cover the codes.

Reviewers: haobo, igor, dhruba, ljin, yhchiang

Reviewed By: haobo

CC: leveldb

Differential Revision: https://reviews.facebook.net/D17001

db/db_test.cc

@@ -3330,6 +3330,7 @@ TEST(DBTest, InPlaceUpdateCallbackNoAction) {
 
 TEST(DBTest, CompactionFilter) {
   Options options = CurrentOptions();
+  options.max_open_files = -1;
   options.num_levels = 3;
   options.max_mem_compaction_level = 0;
   options.compaction_filter_factory = std::make_shared<KeepFilterFactory>();