Set Gerrit to 2.16-rc0

Contextually to the upgrade, fix the javaOptions to the
Gerrit config at startup to make it compatible with
the current default configuration.

Change-Id: I9c0e6745b80be6aee4f090ef8e35e94ad05e293d
diff --git a/centos/7/Dockerfile b/centos/7/Dockerfile
index 85d9cae..2971a23 100644
--- a/centos/7/Dockerfile
+++ b/centos/7/Dockerfile
@@ -9,7 +9,7 @@
 # Install OpenJDK and Gerrit in two subsequent transactions
 # (pre-trans Gerrit script needs to have access to the Java command)
 RUN yum -y install java-1.8.0-openjdk
-RUN yum -y install gerrit-2.15.5-1  && rm -f /var/gerrit/logs/*
+RUN yum -y install gerrit-2.16.rc0-1  && rm -f /var/gerrit/logs/*
 
 USER gerrit
 RUN java -jar /var/gerrit/bin/gerrit.war init --batch --install-all-plugins -d /var/gerrit
diff --git a/ubuntu/16/Dockerfile b/ubuntu/16/Dockerfile
index a90df96..2113475 100644
--- a/ubuntu/16/Dockerfile
+++ b/ubuntu/16/Dockerfile
@@ -12,12 +12,12 @@
 # Install OpenJDK and Gerrit in two subsequent transactions
 # (pre-trans Gerrit script needs to have access to the Java command)
 RUN apt-get -y install openjdk-8-jdk
-RUN apt-get -y install gerrit=2.15.5-1 && rm -f /var/gerrit/logs/*
+RUN apt-get -y install gerrit=2.16.rc0-1 && rm -f /var/gerrit/logs/*
 
 USER gerrit
 RUN java -jar /var/gerrit/bin/gerrit.war init --batch --install-all-plugins -d /var/gerrit
 RUN java -jar /var/gerrit/bin/gerrit.war reindex -d /var/gerrit
-RUN git config -f /var/gerrit/etc/gerrit.config container.javaOptions "-Djava.security.egd=file:/dev/./urandom"
+RUN git config -f /var/gerrit/etc/gerrit.config --add container.javaOptions "-Djava.security.egd=file:/dev/./urandom"
 
 ENV CANONICAL_WEB_URL=