MFC r316695, MFV r316693:
8046 Let calloc() do the multiplication in libzfs_fru_refresh

https://github.com/illumos/illumos-gate/commit/5697e03e6e3e2697f56ae341c7c8ce79680d6a2e

https://www.illumos.org/issues/8046

Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Pedro Giffuni <pfg@freebsd.org>

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

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

Finally... Import the latest open-source ZFS version - (SPA) 28.

Few new things available from now on:

- Data deduplication.
- Triple parity RAIDZ (RAIDZ3).
- zfs diff.
- zpool split.
- Snapshot holds.
- zpool import -F. Allows to rewind corrupted pool to earlier
transaction group.
- Possibility to import pool in read-only mode.

MFC after: 1 month