db 连接 dispatcher 的限定，防止错连、误连

[kaven276]

global.startCfg = {
  listen_port : program.listen_port,
  client_config : program.client_config,
  keep_alive_interval : program.keep_alive_interval || 280,
  db : {
    name : program.db_name,
    domain : program.db_domain,
    unique : program.db_unique_name,
    inst : program.db_instance,
    role : program.db_role,
    cfg_id : program.db_cfg_id
  }
};

  var db = {
    name : headers['x-db_name'],
    domain : headers['x-db_domain'],
    unique : headers['x-db_unique_name'],
    con_name : headers['x-con_name'],
    role : headers['x-database_role'],
    inst : parseInt(headers['x-instance']),
    cfg_id : headers['x-cfg_id']
  };

  for (var n in db) {
    if (startCfg.db[n] && startCfg.db[n] !== db[n]) {
      // todo: add warning
      logLifeCycle('db[%s] not match %s(config) != %s(incoming)', n, startCfg.db[n], db[n]);
      logLifeCycle(db);
      logLifeCycle(startCfg.db);
      return false;
    }
  }