Fixed severe problem with the siamese estimator. Sorry to push this directly...

Fixed severe problem with the siamese estimator. Sorry to push this directly to the master, but this is an emergency. The estimator was super wrong

bob/learn/tensorflow/estimators/Siamese.py

@@ -139,7 +139,7 @@ class Siamese(estimator.Estimator):
                                                               self.extra_checkpoint["scopes"])
     
                 # Compute Loss (for both TRAIN and EVAL modes)
-                self.loss = self.loss_op(prelogits_left, prelogits_left, labels)
+                self.loss = self.loss_op(prelogits_left, prelogits_right, labels)
                
                 # Configure the Training Op (for TRAIN mode)
                 global_step = tf.contrib.framework.get_or_create_global_step()