Pin Docker image java:8

java:8
->
java:8@sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d

[atomist:generated]
[atomist-skill:atomist/docker-base-image-policy]

Author: atomist-bot

examples/helloworld-service-opt-1/Dockerfile

@@ -14,7 +14,7 @@
 # limitations under the License.
 ###############################################################################
 
-FROM java:8
+FROM java:8@sha256:c1ff613e8ba25833d2e1940da0940c3824f03f802c449f3d1815a66b7f8c0e9d
 MAINTAINER Ray Tsang <saturnism@gmail.com>
 
 ENV SRC_DIR /app/src