Use Collection#forEach() instead of Stream#forEach() for simplicity

Change-Id: I0a1aea4bdb5d305c50273e6ff749fe71bd2a295a
diff --git a/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceProvider.java b/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceProvider.java
index 955a657..5934939 100644
--- a/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceProvider.java
+++ b/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceProvider.java
@@ -78,8 +78,7 @@
         rpcRegistry.unregister(this);
 
         // shutdown all channels
-        channels.values().stream()
-            .forEach(ManagedChannel::shutdown);
+        channels.values().forEach(ManagedChannel::shutdown);
         // Should we wait for shutdown? How?
         channels.clear();
         log.info("Stopped");