LU-17179 tests: check the system is clean

LU-17179 tests: check the system is clean

Main part of tests cannot work correctly if the system
is not clean. So check this in the beginning of sanity-quota.

Lustre-change: https://review.whamcloud.com/52630
Lustre-commit: 7e1fb1a296ec7ab21be7ec39e2b6a38fbca76b6c

Test-Parameters: trivial
Signed-off-by: Sergey Cheremencev <scherementsev@ddn.com>
Change-Id: Ibfbe4663dee8476486e96eb99ccbcea13216861b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/59112
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>