MFC r287745: 5997 FRU field not set during pool creation and never

MFC r287745: 5997 FRU field not set during pool creation and never
updated

ZFS already supports storing the vdev FRU in a vdev property.  There
is code in libzfs to work with this property, and there is code in
the zfs-retire FMA module that looks for that information.  But there
is no code actually setting or updating the FRU.

To address this, ZFS is changed to send a handful of new events
whenever a vdev is added, attached, cleared, or onlined, as well
as when a pool is created or imported.

Note that syseventd is not currently available on FreeBSD and thus
some work is needed to actually support the new ZFS events (e.g. in
zfsd) to actually use this capability, this changeset is mostly a
diff reduction from upstream.

illumos/illumos-gate@1437283407f89cab03860accf49408f94559bc34

Illumos issues:

    5997 FRU field not set during pool creation and never updated
    https://www.illumos.org/issues/5997

git-svn-id: svn://svn.freebsd.org/base/stable/10@290745 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f