sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
	When a da or ada device dissappears, outstanding IOs fail with
	ENXIO, not EIO.  The check for EIO was probably copied from Illumos,
	where that is indeed the correct errno.

	Without this change, pulling a busy drive from a zpool would usually
	turn it into UNAVAIL, even though pulling an idle drive would turn
	it into REMOVED.  With this change, it is REMOVED every time.

	Also, vdev_geom_io_intr shouldn't do zfs_post_remove, because that
	results in devd getting two resource.fs.zfs.removed events.  The
	comment said that the event had to be sent directly instead of
	through the async removal thread because "the DE engine is using
	this information to discard prevoius I/O errors".  However, the fact
	that vdev_geom_io_intr was never actually sending the events until
	now, and that vdev_geom_orphan never sent them at all, and that
	vdev_geom_orphan usually gets called about 2 seconds after the
	actual removal, means that FreeBSD's userland can cope with a late
	event just fine.

Approved by:	ken (mentor)
Sponsored by:	Spectra Logic Corporation
MFC after:	4 weeks

(cherry picked from commit 03e85c2d9b2f84dbb1057f11141eae057a835fa2)

Ticket: #3674