ZTS: Cleanup partition tables

The cleanup_devices function should remove any partitions created
on the device and force the partition table to be reread.  This
is needed to ensure that blkid has an up to date version of what
devices and partitions are used by zfs.

The cleanup_devices call was removed from inuse_008_pos.ksh since
it operated on partitions instead of devices and was not needed.

Lastly ddidecode may be called by parted and was therefore added
to the constrained path.

Reviewed-by: Tony Hutter <hutter2@llnl.gov>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #9806

tests/zfs-tests/include/commands.cfg

@@ -132,6 +132,7 @@ export SYSTEM_FILES_LINUX='attr
     blockdev
     chattr
     cksum
+    dmidecode
     exportfs
     fallocate
     fdisk

tests/zfs-tests/include/libtest.shlib

@@ -2301,10 +2301,11 @@ function cleanup_devices #vdevs
 {
 	typeset pool="foopool$$"
 
-	if poolexists $pool ; then
-		destroy_pool $pool
-	fi
+	for vdev in $@; do
+		zero_partitions $vdev
+	done
 
+	poolexists $pool && destroy_pool $pool
 	create_pool $pool $@
 	destroy_pool $pool