ZTS: Fix zpool_import_hostid_changed_cachefile_unclean_export

[behlendorf]

Motivation and Context

https://github.com/openzfs/zfs/actions/runs/11035507045/job/30660961625

  Test (Linux): /usr/share/zfs/zfs-tests/tests/functional/cli_root/zpool_import/zpool_import_hostid_changed_cachefile_unclean_export (run as root) [00:00] [FAIL]
  19:36:30.10 SUCCESS: zgenhostid -f 01234567
  19:36:30.25 SUCCESS: zpool create -o cachefile=/var/tmp/cachefile.483896 testpool1 /var/tmp/dev_import-test/disk0
  19:36:30.26 SUCCESS: cp /var/tmp/cachefile.483896 /var/tmp/cachefile.483896.bkp
  19:36:30.28 SUCCESS: cp /var/tmp/dev_import-test/disk0 /var/tmp/dev_import-test/disk0.bak
  19:36:30.36 SUCCESS: zpool export testpool1
  19:36:30.38 SUCCESS: cp -f /var/tmp/dev_import-test/disk0.bak /var/tmp/dev_import-test/disk0
  19:36:30.38 SUCCESS: rm -f /var/tmp/dev_import-test/disk0.bak
  19:36:30.39 SUCCESS: zgenhostid -f 89abcdef
  19:36:30.46 cachefile import failed, retrying
  19:36:30.46 SUCCESS: zpool import -c /var/tmp/cachefile.483896.bkp testpool1 exited 1
  19:36:30.79 	Recovery is possible, but will result in some data loss.
  19:36:30.79 	Returning the pool to its state as of Wed Sep 25 19:36:30 2024
  19:36:30.79 	should correct the problem.  Recovery can be attempted
  19:36:30.79 	by executing 'zpool import -F testpool1'.  A scrub of the pool
  19:36:30.79 	is strongly recommended after recovery.
  19:36:30.79 cachefile import failed, retrying
  19:36:30.79 	Recovery is possible, but will result in some data loss.
  19:36:30.79 	Returning the pool to its state as of Wed Sep 25 19:36:30 2024
  19:36:30.79 	should correct the problem.  Recovery can be attempted
  19:36:30.79 	by executing 'zpool import -F testpool1'.  A scrub of the pool
  19:36:30.79 	is strongly recommended after recovery.
  19:36:30.79 cannot import 'testpool1': insufficient replicas
  19:36:30.79 cannot import 'testpool1': insufficient replicas
  19:36:30.79 ERROR: zpool import -f -c /var/tmp/cachefile.483896.bkp testpool1 exited 1

Description

Update the test case to freeze the pool then export it to better simulate a hard failure. This is preferable to copying the vdev while the pool's imported since with a copy we're not guaranteed the on-disk state will be consistent. That can in turn result in a pool import failure and a spurious test failure.

How Has This Been Tested?

Will be tested by the CI.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Performance enhancement (non-breaking change which improves efficiency)
• Code cleanup (non-breaking change which makes code smaller or more readable)
• Breaking change (fix or feature that would cause existing functionality to change)
• Library ABI change (libzfs, libzfs_core, libnvpair, libuutil and libzfsbootenv)
• Documentation (a change to man pages or other documentation)

Checklist:

• My code follows the OpenZFS code style requirements.
• I have updated the documentation accordingly.
• I have read the contributing document.
• I have added tests to cover my changes.
• I have run the ZFS Test Suite with this change applied.
• All commit messages are properly formatted and contain Signed-off-by.