Add unit test for fallback route of manifest cache

Test: Run atest
Change-Id: Icc6a2c809c571c3ad8e16a863c37afd8d4042ed6
diff --git a/common/action_processor.h b/common/action_processor.h
index 735a106..ad98cc9 100644
--- a/common/action_processor.h
+++ b/common/action_processor.h
@@ -89,7 +89,7 @@
   // But this call deletes the action if there no other object has a reference
   // to it, so in that case, the caller should not try to access any of its
   // member variables after this call.
-  void ActionComplete(AbstractAction* actionptr, ErrorCode code);
+  virtual void ActionComplete(AbstractAction* actionptr, ErrorCode code);
 
  private:
   FRIEND_TEST(ActionProcessorTest, ChainActionsTest);