LU-13677 quota: qunit sorting doesn't work

LU-13677 quota: qunit sorting doesn't work

As sorting doesn't work correctly, sometimes
new decreased qunit may be not sent to OST.
If qunit reaches it's minimum and is not sent
to OST, this may cause a client to hung on
write as OST gets EINPROGRESS instead of
EDQUOT. Patch solves this issue.

Change-Id: I3ae22cc4d080968132ca762b9c0915a994ac126e
Signed-off-by: Sergey Cheremencev <sergey.cheremencev@hpe.com>
Reviewed-on: https://review.whamcloud.com/38942
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Andreas Dilger <adilger@whamcloud.com>
Reviewed-by: Alexander Boyko <alexander.boyko@hpe.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>