Fix the usage info of cita

[kaikai1024]

Description

FIx the usage about the create & append.

Usage: cita <command> <node> [options]
where <command> is one of the following:
    { help | create | append | port | setup | start | stop
      restart ping | top | backup | clean | logs | logrotate }
Run `cita help` for more detailed information.

[jerry-yu]

done