fixes #4890 - content view filter: unable to add package groups

This commit actually fixes 2 issues:

1. unable to add package groups to a package group filters
2. clicking on Remove/List or Add will generate an invalid
   request to the server (i.e. missing filter id)
Merge pull request #3894 from bbuckingham/issue-4890

fixes #4890 - content view filter: unable to add package groups