8880 improve DTrace error checking

illumos/illumos-gate@2cf374268f3e1c9e9be6367466b183d27632583a
https://github.com/illumos/illumos-gate/commit/2cf374268f3e1c9e9be6367466b183d27632583a

https://www.illumos.org/issues/8880

Reviewed by: Tim Kordas <tim.kordas@joyent.com>
Reviewed by: Bryan Cantrill <bryan@joyent.com>
Reviewed by: Richard Lowe <richlowe@richlowe.net>
Approved by: Dan McDonald <danmcd@joyent.com>
Author: Jerry Jelinek <jerry.jelinek@joyent.com>