LU-17763 tests: use urandom in sanity/66

LU-17763 tests: use urandom in sanity/66

as zfs-2.2.6 compresses data by default and this breaks the test
using /dev/zero as a source.

Test-Parameters: trivial
Test-Parameters: fstype=zfs env=ONLY=66 testlist=sanity
Signed-off-by: Alex Zhuravlev <bzzz@whamcloud.com>
Change-Id: I6853c693e7cb560ae737025507e5377da82c787b
Reviewed-on: https://review.whamcloud.com/c/fs/lustre-release/+/57987
Tested-by: jenkins <devops@whamcloud.com>
Tested-by: Maloo <maloo@whamcloud.com>
Reviewed-by: James Simmons <jsimmons@infradead.org>
Reviewed-by: Timothy Day <timday@amazon.com>
Reviewed-by: Jian Yu <yujian@whamcloud.com>
Reviewed-by: Oleg Drokin <green@whamcloud.com>