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