raidz_test: Fix ZIO ABDs initialization
- When filling ABDs of several segments, consider offset.
- "Corrupt" ABDs with actually different data to fail something.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Rob Norris <robn@despairlabs.com>
Signed-off-by: Alexander Motin <alexander.motin@TrueNAS.com>
Closes #17977