LU-17431 mdt: add ioctl handler for mds

LU-17431 mdt: add ioctl handler for mds

Adding ioctl handler for mds allows managing dynamic nodemaps
on MDS side.

Test-Parameters: trivial
Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
Change-Id: I6a68a17d3f12c799238a93242bbd385e6eeb1d0b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/54504
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>