Fix valgrind failure due to memory leaks

Summary: Test cases for IsBottommostLevel function create FileMetaData objects which were not getting deleted in the destructor.

Test Plan: Valgrind check on compaction_picker_test

Reviewers: yhchiang, igor, sdong

Subscribers: rven, kradhakrishnan, IslamAbdelRahman, dhruba, anthony

Differential Revision: https://reviews.facebook.net/D47463

db/compaction_picker_test.cc

@@ -70,6 +70,12 @@ class CompactionPickerTest : public testing::Test {
   void DeleteVersionStorage() {
     vstorage_.reset();
     files_.clear();
+    for (uint32_t i = 0; i < input_files_.size(); ++i) {
+      for (uint32_t j = 0; j < input_files_[i].files.size(); ++j) {
+        delete input_files_[i].files[j];
+      }
+      input_files_[i].files.clear();
+    }
     input_files_.clear();
   }