Dropping log level of device not having driver for default provider to DEBUG

Change-Id: I79d14ec87ffe24f71407e10f9beb5438c41ac54b
diff --git a/core/net/src/main/java/org/onosproject/net/group/impl/GroupDriverProvider.java b/core/net/src/main/java/org/onosproject/net/group/impl/GroupDriverProvider.java
index 550f245..56b0f97 100644
--- a/core/net/src/main/java/org/onosproject/net/group/impl/GroupDriverProvider.java
+++ b/core/net/src/main/java/org/onosproject/net/group/impl/GroupDriverProvider.java
@@ -65,7 +65,7 @@
         if (device.is(GroupProgrammable.class)) {
             return device.as(GroupProgrammable.class);
         } else {
-            log.warn("Device {} is not group programmable", deviceId);
+            log.debug("Device {} is not group programmable", deviceId);
             return null;
         }
     }