7490 real checksum errors are silenced when zinject is on
illumos/illumos-gate@6cedfc397d6cedfc397dhttps://www.illumos.org/issues/7490
When zinject is on, error codes from zfs_checksum_error() can be overwritten
due to an incorrect and overly-complex if condition.
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Robert Mustacchi <rm@joyent.com>
Author: Pavel Zakharov <pavel.zakharov@delphix.com>
36064ac2d5