Set Gerrit to 2.15.9

Change-Id: I283fe30ab2add17014302ff1ffae745e53800b1d

centos/7/Dockerfile

diff --git a/centos/7/Dockerfile b/centos/7/Dockerfile
index b6b9e3e..97e8151 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-2.15.8-1  && rm -f /var/gerrit/logs/*
+RUN yum -y install gerrit-2.15.9-1  && rm -f /var/gerrit/logs/*
 
 USER gerrit
 RUN java -jar /var/gerrit/bin/gerrit.war init --batch --install-all-plugins -d /var/gerrit

ubuntu/16/Dockerfile

diff --git a/ubuntu/16/Dockerfile b/ubuntu/16/Dockerfile
index b791554..e21402d 100644
--- a/ubuntu/16/Dockerfile
+++ b/ubuntu/16/Dockerfile
@@ -12,7 +12,7 @@
 # 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=2.15.8-1 && rm -f /var/gerrit/logs/*
+RUN apt-get -y install gerrit=2.15.9-1 && rm -f /var/gerrit/logs/*
 
 USER gerrit
 RUN java -jar /var/gerrit/bin/gerrit.war init --batch --install-all-plugins -d /var/gerrit