ONOS-4801 add default available field to gRPC model

- replace deprecated methods with new Protobuf 3 API
- cosmetic changes

Change-Id: I4655fc0fd76c8de83ea03615fc876c5aa9445367
diff --git a/incubator/protobuf/src/main/proto/Device.proto b/incubator/protobuf/src/main/proto/Device.proto
index a01790e..75cf0f5 100644
--- a/incubator/protobuf/src/main/proto/Device.proto
+++ b/incubator/protobuf/src/main/proto/Device.proto
@@ -12,6 +12,7 @@
   string serial_number = 6;
   string chassis_id = 7;
   map<string, string> annotations = 8;
+  bool is_default_available = 9;
 }
 
 enum MastershipRole {
@@ -47,4 +48,4 @@
   string serial_number = 6;
   string chassis_id = 7;
   map<string, string> annotations = 8;
-} 
\ No newline at end of file
+}