Whenever any notice is required to be given under the provisions of this chapter or under the provisions of the articles of incorporation or bylaws of a cooperative, a waiver thereof in writing signed by the persons entitled to such notice, whether before or after the time fixed for the giving of such notice, shall be deemed equivalent to such notice. If a person entitled to notice of a meeting shall attend such meeting, such attendance shall constitute a waiver of notice of the meeting, except in case the attendance is for the express purpose of objecting to the transaction of any business because the meeting shall not have been lawfully called or convened.