MFC r298786 (by asomers):

MFC r298786 (by asomers):
Refactor vdev_geom_attach and friends to reduce code duplication

sys/cddl/contrib/opensolaris/uts/common/fs/zfs/vdev_geom.c
        Move checks for provider's sectorsize and mediasize into a single
        location in vdev_geom_attach. Remove the zfs::vdev::taste class;
        it's ok to use the regular vdev class for tasting. Consolidate guid
        checks into a single location in vdev_attach_ok. Consolidate some
        error handling code from vdev_geom_attach into vdev_geom_detach,
        closing a resource leak of geom consumers in the process.

git-svn-id: svn://svn.freebsd.org/base/stable/10@308058 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f