LU-14687 llite: Return errors for aio

LU-14687 llite: Return errors for aio

The aio code incorrectly discards errors from
ll_direct_rw_pages.  Fix this and add a test for this.

Signed-off-by: Patrick Farrell <farr0186@gmail.com>
Change-Id: I49dadd0b3692820687fa6a1339e00516edf7a5d5
Reviewed-on: https://review.whamcloud.com/43722
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Reviewed-by: Wang Shilong <wshilong@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>