A credit union shall have a lien on the membership shares, share accounts and deposit accounts and accumulated dividends and interest of a member’s individual, joint or trust account for any sum owed the credit union from that member or for any extension of credit endorsed or guaranteed by him. A credit union may refuse to allow withdrawals and shall have a right of immediate set-off with respect to every such account. The board of directors or any person or committee to which it has delegated the authority to extend credit may waive the credit union’s rights to a lien, to immediate set-off, to restrict withdrawals or to any combination of those rights with respect to any share or deposit account or groups of those accounts.