libzfs: use zfs_strerror() in place of strerror()

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Tino Reichardt <milky-zfs@mcmilk.de>
Signed-off-by: Richard Kojedzinszky <richard@kojedz.in>
Closes #15793