OpenZFS 8641 - "zpool clear" and "zinject" don't work on "spare" or "replacing" vdevs

OpenZFS 8641 - "zpool clear" and "zinject" don't work on "spare" or "replacing" vdevs

Add "spare" and "replacing" to the list of interior vdev types in
zpool_vdev_is_interior(), alongside the existing "mirror" and "raidz".
This fixes running "zinject -d" and "zpool clear" on spare and replacing
vdevs.

Authored by: Alan Somers <asomers@gmail.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Melikov <mail@gmelikov.ru>
Approved by: Gordon Ross <gwr@nexenta.com>
Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
OpenZFS-issue: https://www.illumos.org/issues/8641
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/9a36801382
Closes #7060