3743 zfs needs a refcount audit
Submitted by:	Will Andrews <willa@spectralogic.com>
Submitted by:	Justin Gibbs <justing@spectralogic.com>
Reviewed by:	Matthew Ahrens <mahrens@delphix.com>
Reviewed by:	Eric Schrock <eric.schrock@delphix.com>
Reviewed by:	George Wilson <george.wilson@delphix.com>
3744 zfs shouldn't ignore errors unmounting snapshots
Submitted by:	Will Andrews <willa@spectralogic.com>
Reviewed by:	Matthew Ahrens <mahrens@delphix.com>