Gdeproxy convertatomfeed

1. Converted the python deproxy test for identity atom feed cache invalidation to gdeproxy:

python test is located in test/qe/identity-atom-feed
gdeproxy test is located in test/spock-functional-test/src/test/groovy/features/filters/clientauthn/cache

This is using a snapshot (as another bug was found and fixed in gdeproxy).  An official 0.9.4 release of gdeproxy will need to be built first thing.