zfs: don't pretty-print objsetid property

The objsetid property, while being stored as a number, is a dataset
identifier and should not be pretty-printed.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: George Melikov <mail@gmelikov.ru>
Reviewed-by: Chris Dunlop <chris@onthe.net.au>
Signed-off-by: loli10K <ezomori.nozomu@gmail.com>
Closes openzfs#8784

lib/libzfs/libzfs_dataset.c

@@ -31,6 +31,7 @@
  * Copyright 2016 Igor Kozhukhov <ikozhukhov@gmail.com>
  * Copyright 2017-2018 RackTop Systems.
  * Copyright (c) 2019 Datto Inc.
+ * Copyright (c) 2019, loli10K <ezomori.nozomu@gmail.com>
  */
 
 #include <ctype.h>
@@ -2986,8 +2987,10 @@ zfs_prop_get(zfs_handle_t *zhp, zfs_prop_t prop, char *propbuf, size_t proplen,
 
 	case ZFS_PROP_GUID:
 	case ZFS_PROP_CREATETXG:
+	case ZFS_PROP_OBJSETID:
 		/*
-		 * GUIDs are stored as numbers, but they are identifiers.
+		 * These properties are stored as numbers, but they are
+		 * identifiers.
 		 * We don't want them to be pretty printed, because pretty
 		 * printing mangles the ID into a truncated and useless value.
 		 */