MFC ZFS userland to reduce diff with stable/9:

MFC ZFS userland to reduce diff with stable/9:
r224170, r224526, r226583, r226613, r226615, r226616

MFC r224170 (gibbs):
Correct reporting of missing leaf vdevs so that the GUID required to
perform pool actions is always displayed.

cddl/contrib/opensolaris/cmd/zpool/zpool_main.c:
	The "zpool status" command reports the "last seen at"
	device node path when the vdev name is being reported
	by GUID.  Augment this code to assume a GUID is reported
	when a device goes missing after initial boot in addition
	to the previous behavior of doing this for devices that
	aren't seen at boot.

cddl/contrib/opensolaris/lib/libzfs/common/libzfs_pool.c:
	In zpool_vdev_name(), report recently missing devices
	by GUID.  There is no guarantee they will return at
	their previous location.

MFC r224526 (mm, userland part only):
Fix serious bug in ZIL that can lead to pool corruption
in the case of a held dataset during remount.

Detailed description is available at:
https://www.illumos.org/issues/883

illumos-gate revision:	13380:161b964a0e10

MFC r226583 (pjd):
Make all the lines align properly.

MFC r226613 (pjd) [1]:
libzpool task_alloc: pass only valid flags to kmem_alloc

tqflags may contain other flags besided those that are suitable for
kmem_alloc == umem_alloc

MFC r226615 (pjd) [1]:
thr_create: new_thread_ID may be NULL

MFC r226616 (pjd) [1]:
zdb: access dp_free_bpobj only if pool version is >= SPA_VERSION_DEADLISTS

Submitted by:	avg [1]

git-svn-id: svn://svn.freebsd.org/base/stable/8@229664 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f