in the old behavior, the flags is not set, and it will be generated as default value in the first read. so the default value for the latency_first will be set to true according to the Default settings to Flag.
so the Vue code init the latency first to true.
1. remove some unessesary copy in cli parse code of string
2. make some member function into non-member function to avoid taking the self reference.
3. use if let Some(..) instead of if xxx.is_some() to avoid copy and unwrap
