Clean up examples

contrib/Python/cntk/examples/LogReg/logreg.py

@@ -49,9 +49,7 @@ def train_eval_logistic_regression_from_file(criterion_name=None,
     my_sgd = C.SGDParams(
         epoch_size=0, minibatch_size=25, learning_rates_per_mb=0.1, max_epochs=3)
 
-    with C.LocalExecutionContext('logreg') as ctx:
-        ctx.device_id = device_id
-
+    with C.LocalExecutionContext('logreg', device_id=device_id, clean_up=True) as ctx:
         ctx.train(
             root_nodes=[ce, eval], 
             training_params=my_sgd,

contrib/Python/cntk/examples/LogReg/logreg_numpy.py

@@ -69,9 +69,7 @@ def train_eval_logistic_regression_with_numpy(criterion_name=None,
     my_sgd = C.SGDParams(epoch_size=0, minibatch_size=25,
             learning_rates_per_mb=0.1, max_epochs=3)
 
-    with C.LocalExecutionContext('logreg', clean_up=True) as ctx:
-        ctx.device_id = device_id
-
+    with C.LocalExecutionContext('logreg_numpy', device_id=device_id, clean_up=True) as ctx:
         ctx.train(
                 root_nodes=[ce,eval], 
                 training_params=my_sgd)