Deleting a service does not clear the cache of the retrieved items

### Steps to reproduce
- Create an RSS service (e.g. http://pltconfusion.com/rss.xml)
- Wait for at least one element to populate in the admin page.
- Log into the development server
- `redis-cli -n 15`
- `keys *`
- Should be more than 1 item of the following format `cache:jbuilder/v4/brands/1/embeds/1/entities/21-20160301222148-20140713220000/4c3907f92cc7c3be93508ead731d226e`
- Delete the RSS service
- Within the redis command line, do `keys *`
- Should be more than 1 item of the following format `cache:jbuilder/v4/brands/1/embeds/1/entities/21-20160301222148-20140713220000/4c3907f92cc7c3be93508ead731d226e` (even though the items in the db and on the UI have been removed)