CORD-2772 set version number for vtn service

Change-Id: I8374fa9e7aeb03d5e0b769248a5e007c5921c8b2
diff --git a/xos/synchronizer/Dockerfile.synchronizer b/xos/synchronizer/Dockerfile.synchronizer
index 9de9142..0ac8a99 100644
--- a/xos/synchronizer/Dockerfile.synchronizer
+++ b/xos/synchronizer/Dockerfile.synchronizer
@@ -13,6 +13,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
+# This Dockerfile is DEPRECATED and will be removed imminently.
 
 # xosproject/vtn-synchronizer
 FROM xosproject/xos-synchronizer-base:candidate