LU-16927 tests: improve sanity-quota

LU-16927 tests: improve sanity-quota

DD variable already includes "if=/dev/zero"
and "bs=1M". This patch removes double
declaration of 'bs' and/or 'if' when called
with DD

This patch also changes direct 'dd' calls
to use $DD whenever applicable

Also for sanity-quota/52 fix error path variable
name.

Test-Parameters: trivial testlist=sanity-quota
Signed-off-by: Arshad Hussain <arshad.hussain@aeoncomputing.com>
Change-Id: I9006c406f3b794ecdc37a451451538e5202a006a
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/51469
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Sergey Cheremencev <scherementsev@ddn.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>