Any provision in a payment bond attempting by contract to shorten the period prescribed in Section 337 of the Code of Civil Procedure for the commencement of an action on the bond shall not be valid under either of the following circumstances:
(a) If the provision attempts to limit the time for commencement of an action on the bond to a shorter period than six months from the completion of any work of improvement.
(b) As applied to any action brought by a claimant, unless the bond is recorded before the work of improvement is commenced.