Remove redundant toString() calls

Change-Id: I822e9cfe36b7162c7c4fc79e1680c6f54cd64827

@@ -40,7 +40,7 @@ public class TenantIdCodec extends JsonCodec<TenantId> {
         checkNotNull(tenantId, NULL_TENANT_MSG);
 
         ObjectNode result = context.mapper().createObjectNode()
-                .put(TENANT_ID, tenantId.id().toString());
+                .put(TENANT_ID, tenantId.id());
 
         return result;
     }

@@ -144,7 +144,7 @@ public final class Comparators {
     public static final Comparator<DeviceKey> DEVICE_KEY_COMPARATOR = new Comparator<DeviceKey>() {
         @Override
         public int compare(DeviceKey deviceKey1, DeviceKey deviceKey2) {
-            return deviceKey1.deviceKeyId().id().toString().compareTo(deviceKey2.deviceKeyId().id().toString());
+            return deviceKey1.deviceKeyId().id().compareTo(deviceKey2.deviceKeyId().id());
         }
     };
 
@@ -164,7 +164,7 @@ public final class Comparators {
     public static final Comparator<TenantId> TENANT_ID_COMPARATOR = new Comparator<TenantId>() {
         @Override
         public int compare(TenantId tenant1, TenantId tenant2) {
-            return tenant1.id().toString().compareTo(tenant2.id().toString());
+            return tenant1.id().compareTo(tenant2.id());
         }
     };