public Set<String> getAffectedHostNames() {
      return components.stream().map(Component::getHostName).collect(toSet());
    }
Creates and adds stages to the given stage container for deleting kerberos identities.
The service component that belongs to the identity doesn't need to be installed.
ambari-server/src/main/java/org/apache/ambari/server/controller/DeleteIdentityHandler.java