Create IVerifierStatus and add IVerifierStatus.ignored().

verification/try_server.py

Index: verification/try_server.py
diff --git a/verification/try_server.py b/verification/try_server.py
index 60822f751cfa031439544c58898f05609f3f58dd..a5008b8165f3b729691dfee270e5c03e3d54ba8c 100644
--- a/verification/try_server.py
+++ b/verification/try_server.py
@@ -62,7 +62,7 @@ class TryJob(model.PersistentMixIn):
         self.base_url, self.builder, self.build)
 
 
-class TryJobs(model.PersistentMixIn):
+class TryJobs(base.IVerifierStatus):
   """A set of try jobs that were sent for a specific patch."""
   persistent = [
       'try_jobs',
@@ -93,6 +93,9 @@ class TryJobs(model.PersistentMixIn):
         return True
     return False
 
+  def ignored(self):
+    return False
+
 
 class TryRunner(base.Verifier):
   """Stateless communication with a try server.