Checks whether a certain entity type has a certain controller.
string $entity_type: The name of the entity type.
string $controller_type: The name of the controller.
bool Returns TRUE if the entity type has the controller, else FALSE.
public function hasController($entity_type, $controller_type) {
$definition = $this
->getDefinition($entity_type);
return !empty($definition['controllers'][$controller_type]);
}