A savings bank may agree to limit the personal liability of any individual, or of any trustee, partnership, association, corporation or other organization or legal entity, obligated or to be obligated under any bond, note, mortgage or deed of trust insured by the Federal Housing Commissioner, or for which a commitment to insure has been made by the Federal Housing Commissioner, provided that a savings bank may so agree only if the obligations of the commissioner to the savings bank with respect to such insurance or commitment will not be extinguished, reduced or limited by reason of such agreement.