Merge r268024, 268025:

 Fix a case in ndling ATA_PASSTHROUGH commands that have an unaligned buffer.
 This impacts some home-rolled SMART tools.

 In rare cases, a SATA drive can stop responding to commands and trigger a
 reset device task request from the driver.  If the drive fails to respond
 with a signature FIS, the driver would previously get into an endless retry
 loop, stalling all I/O to the drive and keeping user processes stranded.
 Instead, fail the i/o and invalidate the device if the task management
 command times out.  This is controllable with the sysctl and tunable
 hw.isci.fail_on_task_timeout
 dev.isci.0.fail_on_task_timeout

 The default for these is 1.

Obtained from:	Netflix, Inc.