remove cern repo from dockerfile

packaging/docker/Dockerfile

 FROM centos:7
 MAINTAINER CERN
 
-# Add cern repos
-ADD http://linux.web.cern.ch/linux/centos7/CentOS-CERN.repo /etc/yum.repos.d/CentOS-CERN.repo
-ADD http://linuxsoft.cern.ch/cern/centos/7/os/x86_64/RPM-GPG-KEY-CentOS-7 /tmp/RPM-GPG-KEY-cern
-RUN /usr/bin/rpm --import /tmp/RPM-GPG-KEY-cern \
-        && /usr/bin/yum --enablerepo=*-testing clean all \
-        && rm /tmp/RPM-GPG-KEY-cern \
-        && rm -rf /var/cache/yum
-
 #add EPEL repos
 ADD  http://mirror.switch.ch/ftp/mirror/epel/epel-release-latest-7.noarch.rpm  /tmp/epel-release-7.noarch.rpm
 RUN  yum localinstall /tmp/epel-release-7.noarch.rpm -y \