Record physical path information in ZFS Vdevs

Record physical path information in ZFS Vdevs

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c:
	If available, record the physical path of a vdev in ZFS meta-data.
	Do this both when opening the vdev, and when receiving an attribute
	change notification from GEOM.

	Make vdev_geom_close() synchronous instead of deferring its work to
	a GEOM event handler. There is no benefit to deferring the work and
	this prevents a future open call from referencing a consumer that is
	scheduled for destruction. The close followed by an immediate open
	will occur during a vdev reprobe triggered by any type of I/O error.

	Consolidate vdev_geom_close() and vdev_geom_detach() into
	vdev_geom_close() and vdev_geom_close_locked(). This also moves the
	cross linking operations between vdev and GEOM consumer into a
	single place (linking in vdev_geom_attach() and unlinking in
	vdev_geom_close_locked()).

Submitted by:	gibbs, asomers
MFC after:	4 weeks
Sponsored by:	Spectra Logic Corp
Differential Revision:	https://reviews.freebsd.org/D4524