Fix OpenShift resource URI caching - clear cache on service stop

Prevents the cached value from distorting status checks on stopped
resources.

This fixes `infinispan-client` failures observed in e.g.
quarkus-qe/quarkus-test-suite#975.

This is a follow-up to
quarkus-qe#625,
which introduced the caching in order to fix issues in INTEROP
environment. See e.g.
https://mpts-prod.psi.redhat.com/dashboard/run/?id=8896.

quarkus-test-openshift/src/main/java/io/quarkus/test/services/quarkus/OpenShiftQuarkusApplicationManagedResource.java

@@ -74,6 +74,7 @@ public void stop() {
         }
 
         client.scaleTo(model.getContext().getOwner(), 0);
+        uri = null;
         running = false;
     }