[LU-13130] sanity-scrub to use total device size with ZFS

• Type: Improvement
• Resolution: Fixed
• Priority: Trivial
• Fix Version/s: Lustre 2.14.0
• Environment: there is no point to use smaller devices with ZFS as formatting time doesn't depend on device size. on the other hand, ZFS doesn't work very well with tiny devices because of TXG limits, etc.
• Assignee: WC Triage
• Reporter: Alex Zhuravlev