Revert "unskipping bug related to test_stamp_pattern.py"

This reverts commit 60100a3eaec620a8b9946b3378caed6c23122310.

Given the current state of non-deterministic failures in the gate
right now bringing this test back for debugging the failure is just
adding fuel to the fire. We should wait for things to stabilize
again before removing the skip.

Change-Id: Iff5fb31074ddf7dc0e9320ac19ac71fa451a8820