var->save_result.ulong_value was 0 on Mac OS X probably due to positions
of members in the union. sys_var::check() only sets ulonglong_value


sql/set_var.cc:
  Of the save_result union, sys_var::check() only updates ulonglong_value;
  so other types of the union are garbage. Here we must use ulonglong_value
  in sys_var_sync_binlog_period::update(), not ulong_value (which is )