Fix wrong info log printing for num_range_deletions (#5617)

Summary:
num_range_deletions printing is wrong in this log line:

2019/07/18-12:59:15.309271 7f869f9ff700 EVENT_LOG_v1 {"time_micros": 1563479955309228, "cf_name": "5", "job": 955, "event": "table_file_creation", "file_number": 34579, "file_size": 2239842, "table_properties": {"data_size": 1988792, "index_size": 3067, "index_partitions": 0, "top_level_index_size": 0, "index_key_is_user_key": 0, "index_value_is_delta_encoded": 1, "filter_size": 170821, "raw_key_size": 1951792, "raw_average_key_size": 16, "raw_value_size": 1731720, "raw_average_value_size": 14, "num_data_blocks": 199, "num_entries": 121987, "num_deletions": 15184, "num_merge_operands": 86512, "num_range_deletions": 86512, "format_version": 0, "fixed_key_len": 0, "filter_policy": "rocksdb.BuiltinBloomFilter", "column_family_name": "5", "column_family_id": 5, "comparator": "leveldb.BytewiseComparator", "merge_operator": "PutOperator", "prefix_extractor_name": "rocksdb.FixedPrefix.7", "property_collectors": "[]", "compression": "ZSTD", "compression_options": "window_bits=-14; level=32767; strategy=0; max_dict_bytes=0; zstd_max_train_bytes=0; enabled=0; ", "creation_time": 1563479951, "oldest_key_time": 0, "file_creation_time": 1563479954}}

It actually prints "num_merge_operands" number. Fix it.
Pull Request resolved: https://github.com/facebook/rocksdb/pull/5617

Test Plan: Just build.

Differential Revision: D16453110

fbshipit-source-id: fc1024b3cd5650312ed47a1379f0d2cf8b2d8a8f

db/event_helpers.cc

@@ -106,7 +106,7 @@ void EventHelpers::LogAndNotifyTableFileCreationFinished(
               << "num_entries" << table_properties.num_entries
               << "num_deletions" << table_properties.num_deletions
               << "num_merge_operands" << table_properties.num_merge_operands
-              << "num_range_deletions" << table_properties.num_merge_operands
+              << "num_range_deletions" << table_properties.num_range_deletions
               << "format_version" << table_properties.format_version
               << "fixed_key_len" << table_properties.fixed_key_len
               << "filter_policy" << table_properties.filter_policy_name