fixes #6276 / BZ 1106378 - content view package filter - allow user to change existing rules

Without this change, a user cannot modify a package filter rule, if the
change involves going from an equal filter to greater/less/range filter
(or vice versa).

It also allows a user to 'Edit' the filter and then 'Cancel' returning
the entry to it's previous state.
Merge pull request #4321 from bbuckingham/issue-6276

fixes #6276 / BZ 1106378 - content view package filter - allow user to change existing rules