The help message for starting `worker` is `Usage: Worker [options] <master>`. While in `start-slaves.sh`, the format is not align with that, it is confusing for the fist glance.

Author: Zhang, Liye <liye.zhang@intel.com>

Closes #4924 from liyezhang556520/startSlaves and squashes the following commits:

7fd5deb [Zhang, Liye] align arguments order with docs of worker