Illumos #3145, #3212

illumos-gate/commit/9253d63df408bb48584e0b1abfcc24ef2472382e
Illumos changeset: 13840:97fd5cdf328a

3145 single-copy arc
3212 ztest: race condition between vdev_online() and spa_vdev_remove()

Reviewed by: Matt Ahrens <matthew.ahrens@delphix.com>
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Justin T. Gibbs <gibbs@scsiguy.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>

Ported-by: Brian Behlendorf <behlendorf1@llnl.gov>
Issue #989
Issue #1137