app-admin/flannel: mount /etc/hosts ro into flannel container

sdk_container/src/third_party/coreos-overlay/app-admin/flannel/files/flanneld.service

@@ -29,11 +29,13 @@ ExecStart=/usr/bin/rkt run --net=host \
    --volume ssl,kind=host,source=${ETCD_SSL_DIR},readOnly=true \
    --volume certs,kind=host,source=/usr/share/ca-certificates,readOnly=true \
    --volume resolv,kind=host,source=/etc/resolv.conf,readOnly=true \
+   --volume hosts,kind=host,source=/etc/hosts,readOnly=true \
    --mount volume=runsystemd,target=/run/systemd \
    --mount volume=runflannel,target=/run/flannel \
    --mount volume=ssl,target=${ETCD_SSL_DIR} \
    --mount volume=certs,target=/etc/ssl/certs \
    --mount volume=resolv,target=/etc/resolv.conf \
+   --mount volume=hosts,target=/etc/hosts \
    ${FLANNEL_IMG}:${FLANNEL_VER} \
    --exec /opt/bin/flanneld \
    -- --ip-masq=true