Atomic operation instructions are not implemented in s390/ppc
yet. Disabling the testcases for now.

R=machenbach@chromium.org, jkummerow@chromium.org, joransiu@ca.ibm.com, jyan@ca.ibm.com
BUG=
LOG=N

Change-Id: If12ad7886bd517a281efa8c9a3ddfaf3479de68b
Reviewed-on: https://chromium-review.googlesource.com/608488Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Jaideep Bajwa <bjaideep@ca.ibm.com>
Cr-Commit-Position: refs/heads/master@{#47254}