Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Report subcommand handler errors in mfiutil/mptutil so that tools that
invoke the utilities can robustly report errors.

Submitted by: gcooper
Reviewed by: jhb
Approved by: cperciva (mentor)
MFC after: 1 week

Add mptutil, a basic utility for managing MPT SCSI/SATA/SAS controllers.
Drive and controller status can be reported, basic attributes changed,
and arrays and spares can be created and deleted.

Approved by: re
Obtained from: Yahoo! Inc.