A release by the injured person of one joint tort-feasor does not relieve the joint tort-feasor from liability to make contribution to another joint tort-feasor unless the release: Is given before the right of the other tort-feasor to secure a money judgment for contribution has accrued; and Provides for a reduction, to the extent of the pro rata share of the released tort-feasor, of the injured person’s damages recoverable against all other tort-feasors.