As we use etcd's watch interface, we do not need the
network notifications as they are no-ops anyway.
Bonus: Remove globalEtcdClient global usage in IAM
This change allows a set of MinIO sites (clusters) to be configured
for mutual replication of all buckets (including bucket policies, tags,
object-lock configuration and bucket encryption), IAM policies,
LDAP service accounts and LDAP STS accounts.