While #10121 did fix the signal numbers for FreeBSD/Darwin, it
incorrectly changed the expected encoding of exit status for commands
that exited on a signal. The encoding 256+signum is a feature of the
shell. Only the signal numbers themselves are platform-dependent.
Always use the encoding 256+signum when checking exit status for
signal exits.
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Ryan Moeller <ryan@iXsystems.com>
Closes#10137