Content View Definition Filter: fix product removal

Removing a product from the filter was not actually removing
the product.
974712: Content View Filter: improve behavior for repo section

This commit provides a couple of small changes to help improve
the user behavior for filters:

1. when user opens a filter, if it doesn't have any products
   or repositories assigned to it, make the Repositories
   tab the 'active' tab

2. when user goes to the 'Rules' tab, if there aren't any
   products or repositories assigned, present the user a warning
   that they need to add one.
Merge pull request #2971 from bbuckingham/974712

974712: Content View Filter: improve behavior for repo section