Update Dockerfile parent version

Change-Id: Ibe738da9b636e46736d5f4854d113aff898ab2db
diff --git a/Dockerfile.synchronizer b/Dockerfile.synchronizer
index c306da7..9ce94b8 100644
--- a/Dockerfile.synchronizer
+++ b/Dockerfile.synchronizer
@@ -14,7 +14,7 @@
 
 # xosproject/simpleexampleservice-synchronizer
 
-FROM xosproject/xos-synchronizer-base:2.0.0
+FROM xosproject/xos-synchronizer-base:2.1.5
 
 COPY xos/synchronizer /opt/xos/synchronizers/simpleexampleservice
 COPY VERSION /opt/xos/synchronizers/simpleexampleservice/