LU-13835 llite: reuse same cl_dio_aio for one IO

LU-13835 llite: reuse same cl_dio_aio for one IO

IO might be restarted if layout changed, this might
cause ki_complete() called several times for one IO.

Fixes: d1dded6 ("LU-4198 clio: AIO support for direct IO")
Fixes: 84c3e85 ("LU-13697 llite: fix short io for AIO")
Signed-off-by: Wang Shilong <wshilong@ddn.com>
Change-Id: I791b8f9d82fae6822d38293ba22adf74560c9dce
Reviewed-on: https://review.whamcloud.com/39542
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Bobi Jam <bobijam@hotmail.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>