Fixed compilation error.

storage/ndb/src/mgmsrv/InitConfigFileParser.cpp:
  Added 'const' to fix compilation error.

storage/ndb/src/mgmsrv/InitConfigFileParser.cpp

@@ -702,7 +702,7 @@ load_defaults(Vector<struct my_option>& options, const char* groups[])
   BaseString group_suffix;
 
   const char *save_file = my_defaults_file;
-  char *save_extra_file = my_defaults_extra_file;
+  const char *save_extra_file = my_defaults_extra_file;
   const char *save_group_suffix = my_defaults_group_suffix;
 
   if (my_defaults_file)