Surpress excess warning messages

Don't ask for role of NONE when a device is disconnected and role is
already NONE

Change-Id: Ib86335cc17847c820c33743897ae087765271be9
diff --git a/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java b/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
index a86b50d..a3dbcad 100644
--- a/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
+++ b/core/net/src/main/java/org/onosproject/net/device/impl/DeviceManager.java
@@ -766,7 +766,12 @@
         final boolean isReachable = isReachable(did);
         if (!isReachable) {
             // device is not connected to this node
-            if (myNextRole != NONE) {
+            if (mastershipService.getLocalRole(did) == NONE) {
+                log.debug("Node was instructed to be {} role for {}, "
+                                + "but this node cannot reach the device "
+                                + "and role is already None. Ignoring request.",
+                        myNextRole, did);
+            } else if (myNextRole != NONE) {
                 log.warn("Node was instructed to be {} role for {}, "
                                  + "but this node cannot reach the device.  "
                                  + "Relinquishing role.  ",