Refactor Comparator class to break dependency of core/net on the CLI

Change-Id: I6f3165f399ab448eff5c5d2232f4b96f10ebf57e
diff --git a/cli/src/main/java/org/onosproject/cli/MastersListCommand.java b/cli/src/main/java/org/onosproject/cli/MastersListCommand.java
index 8675a3c..7be9d09 100644
--- a/cli/src/main/java/org/onosproject/cli/MastersListCommand.java
+++ b/cli/src/main/java/org/onosproject/cli/MastersListCommand.java
@@ -24,6 +24,7 @@
 import org.onosproject.cluster.ControllerNode;
 import org.onosproject.mastership.MastershipService;
 import org.onosproject.net.DeviceId;
+import org.onosproject.utils.Comparators;
 
 import java.util.Collections;
 import java.util.List;