Disable platform_Powerwash on peppy.

After a powerwash test on a peppy, the firmware doesn't find a
kernel to boot from due to a bug. To avoid breaking all the peppy
devices on the lab we disable the test until issue 337574 is fixed.

BUG=chromium:337574
TEST=test_that --fast -b daisy $DUT platform_Powerwash

Change-Id: I9d55597b19774a3b5f258ad86d92019a5ad779c7
Reviewed-on: https://chromium-review.googlesource.com/183755
Reviewed-by: Alex Miller <milleral@chromium.org>
Tested-by: Alex Deymo <deymo@chromium.org>
Commit-Queue: Alex Deymo <deymo@chromium.org>
diff --git a/server/site_tests/platform_Powerwash/platform_Powerwash.py b/server/site_tests/platform_Powerwash/platform_Powerwash.py
index 7d47616..47e589e 100644
--- a/server/site_tests/platform_Powerwash/platform_Powerwash.py
+++ b/server/site_tests/platform_Powerwash/platform_Powerwash.py
@@ -22,6 +22,12 @@
     version = 1
 
     def run_once(self, host):
+        # TODO(deymo): Remove this once we fix crbug.com/337574
+        host_board = host.get_board().split(':', 1)[1]
+        if host_board == 'peppy':
+            logging.error('Not running on peppy due to http://crbug.com/337574')
+            raise error.TestNAError('Test disabled on peppy.')
+
         self._host = host
 
         count_before = self._powerwash_count()