Unless expressly limited in a will, deed, or other instrument creating a power of sale or unless specifically otherwise provided in such instrument, a power of sale conferred upon an executor, trustee, guardian, or attorney in fact shall authorize a private sale by the executor, trustee, guardian, or attorney in fact, with or without advertisement and on such terms and conditions as the donee of the power may deem advisable, without the necessity of applying for leave to sell or obtaining any order therefor from any court; provided, however, that this Code section shall not apply to powers of sale in security deeds, mortgages, trust deeds, bills of sale, and other instruments conveying property or creating a lien thereon, to secure a debt or debts.