ZTS: Misc fixes for FreeBSD

ZTS: Misc fixes for FreeBSD

* Set geom debug flags in corrupt_blocks_at_level
* Use the right time zone for history tests
* Add missing commands.cfg entry for diskinfo
* Rewrite get_last_txg_synced to use zdb
* Don't check ulimits for sparse files
* Suspend removal before removing a vdev, not after

Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes #10054