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/GrpcRemoteServiceServer.java b/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceServer.java
index 099ed20..260a709 100644
--- a/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceServer.java
+++ b/incubator/rpc-grpc/src/main/java/org/onosproject/incubator/rpc/grpc/GrpcRemoteServiceServer.java
@@ -143,8 +143,7 @@
             Thread.currentThread().interrupt();
         }
 
-        registeredProviders.stream()
-            .forEach(deviceProviderRegistry::unregister);
+        registeredProviders.forEach(deviceProviderRegistry::unregister);
 
         server.shutdown();
         // Should we wait for shutdown?