Add `yum/dnf clean all` to dockerfiles

In a rather desperate try to shrink our container images this commit
adds `yum/dnf clean all` as part of the building process. This helps to
save around 100 MB in case of centos-based images.

Change-Id: I2aaadab4ffec6e0ad744e82fc9145cd86e14a224

cni.Dockerfile

@@ -15,6 +15,7 @@ RUN pip install -c $UPPER_CONSTRAINTS_FILE /opt/kuryr-kubernetes \
     && mkdir -p /etc/kuryr-cni \
     && cp /opt/kuryr-kubernetes/etc/cni/net.d/* /etc/kuryr-cni \
     && yum -y history undo last \
+    && yum clean all \
     && rm -rf /opt/kuryr-kubernetes \
     && mkdir ${OSLO_LOCK_PATH}
 

cni_py3.Dockerfile

@@ -16,6 +16,7 @@ RUN python3.6 -m ensurepip \
     && mkdir -p /etc/kuryr-cni \
     && cp /opt/kuryr-kubernetes/etc/cni/net.d/* /etc/kuryr-cni \
     && dnf -y history undo last \
+    && dnf clean all \
     && rm -rf /opt/kuryr-kubernetes \
     && mkdir ${OSLO_LOCK_PATH}
 

controller.Dockerfile

@@ -11,6 +11,7 @@ COPY . /opt/kuryr-kubernetes
 
 RUN pip install -c $UPPER_CONSTRAINTS_FILE --no-cache-dir /opt/kuryr-kubernetes \
     && yum -y history undo last \
+    && yum clean all \
     && rm -rf /opt/kuryr-kubernetes \
     && groupadd -r kuryr -g 711 \
     && useradd -u 711 -g kuryr \

controller_py3.Dockerfile

@@ -12,6 +12,7 @@ COPY . /opt/kuryr-kubernetes
 RUN python3.6 -m ensurepip \
     && python3.6 -m pip install -c $UPPER_CONSTRAINTS_FILE --no-cache-dir /opt/kuryr-kubernetes \
     && dnf -y history undo last \
+    && dnf clean all \
     && rm -rf /opt/kuryr-kubernetes \
     && groupadd -r kuryr -g 711 \
     && useradd -u 711 -g kuryr \