3745 zpool create should treat -O mountpoint and -m the same
Submitted by:	Will Andrews <willa@spectralogic.com>
Submitted by:	Alan Somers <alans@spectralogic.com>
Reviewed by:	Matthew Ahrens <mahrens@delphix.com>
ztest_deadman_thread(): Account for -T option.

Instead of hardcoding the grace period to 300 seconds, use the
zo_time field, so it can be run for longer if desired, without
tripping the deadman thread.
Strengthen dbuf_free_range() by asserting dn_struct_rwlock.

Update one caller of the dbuf_rm_spill() API so that this can be done.

Submitted by:	Justin Gibbs <justing@spectralogic.com>
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>
3744 zfs shouldn't ignore errors unmounting snapshots
Submitted by:	Will Andrews <willa@spectralogic.com>
Reviewed by:	Matthew Ahrens <mahrens@delphix.com>