Solution for GPCODECOVERAGE-47

Grails controller field values are accessed by the post-test closure replacement procedures.
Noticeable during integration tests, controllers are injected with additional fields from classes such as CommonWebApi.
Some of these fields (such as the application context) cannot be accessed outside a request context, so they throw an exception during the replacement procedure.

Solution: added an iteration filter so that values are retrieved only for property descriptors of type Closure