LU-17334 lmv: exclude newly added MDT in mkdir

LU-17334 lmv: exclude newly added MDT in mkdir

Exclude newly added MDT in QoS mkdir for 30 seconds in case
connections between MDTs are not ready, which may cause lookup fail.

Signed-off-by: Lai Siyao <lai.siyao@whamcloud.com>
Change-Id: Ibb5e6eda29ddfff8f66708d72e33453a96f5e7ef
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/53860
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Hongchao Zhang <hongchao@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>