LU-6142 mdt: remove unused field mti_wait_info.

LU-6142 mdt: remove unused field mti_wait_info.

This field is neither set nor accessed.

Test-Parameters: trivial
Signed-off-by: Mr NeilBrown <neilb@suse.com>
Change-Id: I7b8ccd97ad1228bbd4e8577a6d6003a9888f9282
Reviewed-on: https://review.whamcloud.com/35921
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Tested-by: jenkins <devops@whamcloud.com>
Reviewed-by: Shaun Tancheff <stancheff@cray.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Arshad Hussain <arshad.super@gmail.com>
Reviewed-by: Mike Pershin <mpershin@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>