Fixed old lint errors in db/filename.h

Summary: Fixed old lint errors in db/filename.h

Test Plan: make

Reviewers: igor, sdong, anthony, IslamAbdelRahman

Reviewed By: IslamAbdelRahman

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D47439

db/filename.h

@@ -102,11 +102,13 @@ struct InfoLogPrefix {
 
 // Return the name of the info log file for "dbname".
 extern std::string InfoLogFileName(const std::string& dbname,
-    const std::string& db_path="", const std::string& log_dir="");
+                                   const std::string& db_path = "",
+                                   const std::string& log_dir = "");
 
 // Return the name of the old info log file for "dbname".
 extern std::string OldInfoLogFileName(const std::string& dbname, uint64_t ts,
-    const std::string& db_path="", const std::string& log_dir="");
+                                      const std::string& db_path = "",
+                                      const std::string& log_dir = "");
 
 // Return the name to use for a metadatabase. The result will be prefixed with
 // "dbname".