Verify jenkins.war with sha256 instead of sha1

Jenkins provides a sha256 digest to verify the war file against [1] - we
should be using this instead of the sha1 we generate locally.

[1] https://get.jenkins.io/war-stable/2.222.4/

Bug: Issue 16464
Change-Id: Iecf430c110bbadecda73d98ee9b12d6f24379536
diff --git a/jenkins-docker/server/Dockerfile b/jenkins-docker/server/Dockerfile
index 0d5c329..48b6602 100644
--- a/jenkins-docker/server/Dockerfile
+++ b/jenkins-docker/server/Dockerfile
@@ -4,7 +4,7 @@
 USER root
 
 ARG JENKINS_WAR_SHA
-RUN echo "$JENKINS_WAR_SHA /usr/share/jenkins/jenkins.war" | sha1sum -c -
+RUN echo "$JENKINS_WAR_SHA /usr/share/jenkins/jenkins.war" | sha256sum -c -
 
 # Override Jenkins start-up script
 RUN mv /usr/local/bin/jenkins.sh /usr/local/bin/run-jenkins.sh
diff --git a/jenkins-docker/server/Makefile b/jenkins-docker/server/Makefile
index c2866eb..6c6f8d7 100644
--- a/jenkins-docker/server/Makefile
+++ b/jenkins-docker/server/Makefile
@@ -7,7 +7,8 @@
 JENKINS_API_USER=user
 JENKINS_API_PASSWORD=pass
 JENKINS_WAR_VER=2.222.4
-JENKINS_WAR_SHA=09eff5456a24af88111d4489b99433f24f26b81c
+# https://get.jenkins.io/war-stable/2.222.4/
+JENKINS_WAR_SHA=6c95721b90272949ed8802cab8a84d7429306f72b180c5babc33f5b073e1c47c
 JENKINS_HOME?=~/jenkins_home
 DOCKER_GID?=993
 IMAGE=${ORGANISATION}/${NAME}:${JENKINS_WAR_VER}