FIX: flaky post action counts specs (#27165)

After flags were moved to the database, with each save they are changing available PostActionTypes. Therefore, flag specs should clear the state before and after each example not just before.

In addition, we need to clear `nil` counts for dynamically created flags from serializer.

app/serializers/post_serializer.rb

@@ -331,7 +331,7 @@ class PostSerializer < BasicPostSerializer
         summary[:count] = summary[:acted] ? 1 : 0
       end
 
-      summary.delete(:count) if summary[:count] == 0
+      summary.delete(:count) if summary[:count].to_i.zero?
 
       # Only include it if the user can do it or it has a count
       result << summary if summary[:can_act] || summary[:count]