Try to produce smaller images

reposync/Dockerfile

 FROM cern/cc7-base
 
-RUN yum install -y jq
+RUN yum install -y jq \
+  && yum clean all
 
 RUN rm -rf /etc/yum.repos.d
 COPY yum.repos.d /etc/yum.repos.d/

scheduler/Dockerfile

@@ -2,15 +2,15 @@ FROM cern/cc7-base
 
 ENV NOMAD_VERSION 0.8.4
 
-RUN yum install -y jq unzip
+RUN yum install -y jq unzip \
+  && yum clean all
 
 ADD https://releases.hashicorp.com/nomad/${NOMAD_VERSION}/nomad_${NOMAD_VERSION}_linux_amd64.zip /tmp/nomad.zip
-RUN unzip /tmp/nomad.zip -d /usr/local/bin/
+RUN unzip /tmp/nomad.zip -d /usr/local/bin/ \
+  && rm -rf /etc/yum.repos.d
 
-RUN rm -rf /etc/yum.repos.d
 COPY yum.repos.d /etc/yum.repos.d/
-COPY repos.json /root/
-COPY schedulereposync.sh /root/
+COPY repos.json schedulereposync.sh /root/
 
 WORKDIR /root