Revert "Turn off double updates in VM tests."

These tests were disabled until we fixed the postinst firmware problem...
it's now fixed.

This reverts commit 360bdea5240649b5c3d858bfcc0b53753d0cf321.

BUG=None
TEST=trybot

Change-Id: Id17f9f343ab76fb1a1ceb03f2e4761310f5eadac
Reviewed-on: https://gerrit.chromium.org/gerrit/21577
Tested-by: Don Garrett <dgarrett@chromium.org>
Reviewed-by: David James <davidjames@chromium.org>
Commit-Ready: Don Garrett <dgarrett@chromium.org>
diff --git a/au_test_harness/au_test.py b/au_test_harness/au_test.py
index b961809..1f7ef14 100644
--- a/au_test_harness/au_test.py
+++ b/au_test_harness/au_test.py
@@ -108,10 +108,9 @@
     self.worker.PerformUpdate(self.target_image_path, self.base_image_path)
     self.assertTrue(self.worker.VerifyImage())
 
-    # TODO(dgarrett): Doing and verifying a double update is good...
-    #                 after binary postinst works for this on VMs.
-    #self.worker.PerformUpdate(self.target_image_path, self.target_image_path)
-    #self.assertTrue(self.worker.VerifyImage())
+    # Update from
+    self.worker.PerformUpdate(self.target_image_path, self.target_image_path)
+    self.assertTrue(self.worker.VerifyImage())
 
   def testUpdateWipeStateful(self):
     """Tests if we can update after cleaning the stateful partition.
@@ -129,6 +128,11 @@
                               'clean')
     self.assertTrue(self.worker.VerifyImage())
 
+    # Update from
+    self.worker.PerformUpdate(self.target_image_path, self.target_image_path,
+                              'clean')
+    self.assertTrue(self.worker.VerifyImage())
+
   def testInterruptedUpdate(self):
     """Tests what happens if we interrupt payload delivery 3 times."""