Do not overwrite the default search controls when resolving LDAP Tree References

NXP-18078 introduced a different behavior for the method LDAPDirectory#getSearchControls: now by default the default search controls are returned when we don't want to fetch all the attributes.

Because LDAPTreeReference changes the scope of the search controls, it changed the scope for all the requests which did not want to fetch all the attributes and which used the default search controls.

We need to return a new SearchControls object for the LDAPTreeReference requests