Eliminate Waltz admin protocol

Because we decide to add 32 (or 64) bit Flags to distinguish a regular request from an admin request, like
```
public HelloRequest(String greeting, Flags flags) {
 this.greeting = greeting;
 this.flags = flags;
}
```
admin protocol is not needed anymore. So, we want to
> 1) eliminate Waltz admin handler and admin port
> 2) instead use `Flags` to replace existing admin related request.
