Update docker openjdk image

Current JDK image sourced from dockerhub (java:openjdk-8) is being
deprecated (see https://hub.docker.com/_/java/). Update the relevent
docker file to use the new openjdk:8 image.

Change-Id: Idf9bac8ac6f981ea6e0311190365f37f98915666
Signed-off-by: Julian Carrivick <cjulian@au1.ibm.com>

images/javaenv/Dockerfile.in

@@ -1,9 +1,9 @@
-FROM  java:openjdk-8
+FROM openjdk:8
 RUN wget https://services.gradle.org/distributions/gradle-2.12-bin.zip -P /tmp --quiet
 RUN unzip -q /tmp/gradle-2.12-bin.zip -d /opt && rm /tmp/gradle-2.12-bin.zip
 RUN ln -s /opt/gradle-2.12/bin/gradle /usr/bin
 ADD javashimsrc.tar.bz2 /root
 ADD protos.tar.bz2 /root
 WORKDIR /root
-# Build java shim after copying proto files from fabric/proto  
+# Build java shim after copying proto files from fabric/proto
 RUN core/chaincode/shim/java/javabuild.sh