Fix zfs_upgraded tests for zpool version 5000

tests/sys/cddl/zfs/tests/cli_root/zfs_upgrade/zfs_upgrade.kshlib
Fix default_check_zfs_upgrade and default_setup_datasets
for zpool version 5000

tests/sys/cddl/zfs/tests/cli_root/zpool_upgrade/zpool_upgrade_test.sh
Reenable zpool_upgrade_007_pos. It passed more than 300
times, so the panic that it previously caused has
probably been fixed.

Sponsored by: Spectra Logic Corp