Update analyze_logs.py (#5479)

Author: Y-M-Y

tools/analysis_tools/analyze_logs.py

@@ -65,7 +65,7 @@ def plot_curve(log_dicts, args):
             else:
                 xs = []
                 ys = []
-                num_iters_per_epoch = log_dict[epochs[0]]['iter'][-1]
+                num_iters_per_epoch = log_dict[epochs[0]]['iter'][-2]
                 for epoch in epochs:
                     iters = log_dict[epoch]['iter']
                     if log_dict[epoch]['mode'][-1] == 'val':