Replace Stream#forEach() with Collection#forEach()

Change-Id: I2b261c3d91d345907b165bd61eb7b6c45011c247
diff --git a/utils/misc/src/main/java/org/onlab/util/PredictableExecutor.java b/utils/misc/src/main/java/org/onlab/util/PredictableExecutor.java
index 836d3ae..eb1502d 100644
--- a/utils/misc/src/main/java/org/onlab/util/PredictableExecutor.java
+++ b/utils/misc/src/main/java/org/onlab/util/PredictableExecutor.java
@@ -137,7 +137,7 @@
 
     @Override
     public void shutdown() {
-        backends.stream().forEach(ExecutorService::shutdown);
+        backends.forEach(ExecutorService::shutdown);
     }
 
     @Override