Add etcd path prefix for all IAM assets (#8569)

Currently, we use the top-level prefix "config/"
for all our IAM assets, instead of to provide
tenant-level separation bring 'path_prefix'
to namespace the access properly.

Fixes #8567

cmd/iam-etcd-store.go

@@ -549,6 +549,7 @@ func (ies *IAMEtcdStore) watch(sys *IAMSys) {
 			// Refresh IAMSys with etcd watch.
 			watchCh := ies.client.Watch(context.Background(),
 				iamConfigPrefix, etcd.WithPrefix(), etcd.WithKeysOnly())
+
 			for {
 				select {
 				case <-GlobalServiceDoneCh: