LU-16529 test: wait quota synced on quota slaves

LU-16529 test: wait quota synced on quota slaves

Check and wait the quota setting to be synchronized on
quota slaves before running actual sanity-quota test_84.

Lustre-change: https://review.whamcloud.com/50197
Lustre-commit: TBD (from 0a94395230e7482029ff03381bf77b4783a93e2d)

Test-Parameters: trivial testlist=sanity-quota env=ONLY=84,ONLY_REPEAT=100
Fixes: a2fd4d3aee ("LU-15880 quota: fix insane grant quota")
Signed-off-by: Hongchao Zhang <hongchao@whamcloud.com>
Change-Id: I7752bff33f24d1d38dc340b2addbfc98d6f7c857
Reviewed-on: https://review.whamcloud.com/c/ex/lustre-release/+/50445
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>