Merge branch 'fix-rbd-options-parse' of https://github.com/ketor/fio

Merge branch 'fix-rbd-options-parse' of https://github.com/ketor/fio

Ketor writes:

There is two bug in the rbd_options parse:
1. The memeber struct thread_data *td of struct rbd_options is filled in
the cmdline parse process.So it is usable and cannot be deleted.

2.The busy_poll offset of struct rbd_options is not the "busy_poll" but
"client_name"

After fix these two bugs, the fio test then can run.