Update HibernateFilterFilters.groovy

At least makes it possible to have webflow plugin and hibernate filter in the same project even if it still does not work to use them in the same controller. 

Help me out here, this code is far from perfect but it is the best I can do to get things running at all.

Basically the same changes as proposed by Aaron Long earlier, but that was never sent as a pull request so I make a new try to get some attention.

https://github.com/longwa/grails-hibernate-filter/commit/25096b1265050d61b4069777370489b36b599039