Upgrade tf version to fix security warning (#2113)

* upgrade tf version to fix security warnings

* updates

* updates

* updates

* updates

* updates

* updates

* updates
Co-authored-by: liuzhe-lz <40699903+liuzhe-lz@users.noreply.github.com>

examples/trials/ga_squad/requirements.txt

-tensorflow==1.13.1
+tensorflow==1.15.2

examples/trials/network_morphism/FashionMNIST/FashionMNIST_keras.py

@@ -152,7 +152,7 @@ class SendMetrics(keras.callbacks.Callback):
         if logs is None:
             logs = dict()
         logger.debug(logs)
-        nni.report_intermediate_result(logs["val_acc"])
+        nni.report_intermediate_result(logs["val_accuracy"])
 
 
 # Training

examples/trials/network_morphism/cifar10/cifar10_keras.py

@@ -152,7 +152,9 @@ class SendMetrics(keras.callbacks.Callback):
         if logs is None:
             logs = dict()
         logger.debug(logs)
-        nni.report_intermediate_result(logs["val_acc"])
+        # accuracy key for keras 2.2.2: val_acc
+        # for keras 2.3.1: val_accuracy
+        nni.report_intermediate_result(logs["val_accuracy"])
 
 
 # Training

examples/trials/network_morphism/requirements.txt

 numpy==1.14.2
-tensorflow==1.13.1
+tensorflow==1.15.2
 torchvision==0.2.1
-Keras==2.2.2
+Keras==2.3.1
 torch==0.4.1