rest: add a test on GETing a non existent archive policy
rest: add a test on GETing a non existent archive policy

Change-Id: Ifac345f5eaf9d25d76817d45d885e7da2e689e64

leandroreox/gnocchi,idegtiarov/gnocchi-rep,gnocchixyz/gnocchi,sileht/gnocchi,sileht/gnocchi,leandroreox/gnocchi,idegtiarov/gnocchi-rep,idegtiarov/gnocchi-rep,gnocchixyz/gnocchi