Set Gerrit to 3.0.0-rc0

Change-Id: Ic1623d1bc907e70e68ae60d608866d793530cd8c
diff --git a/centos/7/Dockerfile b/centos/7/Dockerfile
index 40b8f1e..3f8790a 100644
--- a/centos/7/Dockerfile
+++ b/centos/7/Dockerfile
@@ -8,7 +8,7 @@
 # (pre-trans Gerrit script needs to have access to the Java command)
 RUN yum -y install initscripts && \
     yum -y install java-1.8.0-openjdk && \
-    yum -y install gerrit-2.16.5-1  && rm -Rf /var/gerrit/{logs,tmp}/* && rm -Rf /var/gerrit/.gerritcodereview && \
+    yum -y install gerrit-3.0.0.rc0-1  && rm -Rf /var/gerrit/{logs,tmp}/* && rm -Rf /var/gerrit/.gerritcodereview && \
     yum -y clean all
 
 USER gerrit
diff --git a/ubuntu/18/Dockerfile b/ubuntu/18/Dockerfile
index 3981114..495ce8f 100644
--- a/ubuntu/18/Dockerfile
+++ b/ubuntu/18/Dockerfile
@@ -14,7 +14,7 @@
 # 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=2.16.5-1 && rm -f /var/gerrit/logs/*
+RUN apt-get -y install gerrit=3.0.0.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