HACK: Disable secure discard

Summary:
Depends on D268
  - Secure discard is causing wipes to take insane amounts of time.
  - Enable this workaround until the problem is sorted.

Test Plan: verified on hammerhead

Reviewers: randall.rushing, jriordan001, rlasalle15, synergy

Reviewed By: synergy

Differential Revision: http://review.codefirex.com/D269