ECOG Intergroup Randomized Phase III Study of Postoperative Oxaliplatin; 5-Fluorouracil; and Leucovorin vs Oxaliplatin; 5-Fluorouracil; Leucovorin and Bevacizumab for Patients with Stage II or III Rectal Cancer Receiving Pre-Operative Chemoradiation Adult CIRB - Late Phase Emphasis Completed Completed