Fix gate-utils image build job

- Use ubuntu:focal as a base image
- Do not build the gate-utils image weekly.
  The only place we use this image is in the
  kube-node-subnet.sh script where we use the
  image published a while ago.
  And the only package we install into this image
  is ipcalc.

Change-Id: I06dfaef2e429f690b8ca7583933fa85eabcbfea8

gate-utils/Dockerfile.debian

@@ -1,4 +0,0 @@
-ARG FROM=gcr.io/google-containers/debian-base-amd64:0.3
-FROM ${FROM}
-
-RUN /usr/local/bin/clean-install ipcalc

gate-utils/Dockerfile.suse_15

@@ -1,5 +0,0 @@
-ARG FROM=docker.io/opensuse/leap:15
-FROM ${FROM}
-LABEL maintainers=stephane@alum.mit.edu
-
-RUN zypper install -y ipcalc

gate-utils/Dockerfile.ubuntu_focal

@@ -0,0 +1,12 @@
+ARG FROM=ubuntu:focal
+FROM ${FROM}
+
+RUN apt-get update \
+    && apt-get install -y --no-install-recommends ipcalc \
+    && apt-get clean -y \
+    && rm -rf \
+        /var/cache/debconf/* \
+        /var/lib/apt/lists/* \
+        /var/log/* \
+        /tmp/* \
+        /var/tmp/*

gate-utils/build.sh

@@ -6,7 +6,7 @@ cd ${SCRIPT_DIR}/..
 
 IMAGE="gate-utils"
 VERSION=${VERSION:-latest}
-DISTRO=${DISTRO:-debian}
+DISTRO=${DISTRO:-ubuntu_focal}
 REGISTRY_URI=${REGISTRY_URI:-"openstackhelm/"}
 EXTRA_TAG_INFO=${EXTRA_TAG_INFO:-""}
 docker build -f ${IMAGE}/Dockerfile.${DISTRO} --network=host -t ${REGISTRY_URI}${IMAGE}:${VERSION}-${DISTRO}${EXTRA_TAG_INFO} ${extra_build_args} ${IMAGE}

zuul.d/gate-utils.yaml

@@ -23,9 +23,6 @@
     promote:
       jobs:
         - openstack-helm-images-promote-gate-utils
-    periodic-weekly:
-      jobs:
-        - openstack-helm-images-build-gate-utils
 
 - job:
     name: openstack-helm-images-build-gate-utils
@@ -34,18 +31,12 @@
     vars: &gate-utils_vars
       currentdate: "{{ now(utc=True,fmt='%Y%m%d') }}"
       docker_images:
-        #- context: gate-utils
-        #  repository: openstackhelm/gate-utils
-        #  tags:
-        #    - latest-opensuse_15
-        #    - "opensuse_15-{{ currentdate }}"
-        #  dockerfile: Dockerfile.suse_15
         - context: gate-utils
           repository: openstackhelm/gate-utils
-          dockerfile: Dockerfile.debian
+          dockerfile: Dockerfile.ubuntu_focal
           tags:
-            - latest-debian
-            - "debian-{{ currentdate }}"
+            - latest-ubuntu_focal
+            - "ubuntu_focal-{{ currentdate }}"
     files: &gate-utils_files
       - gate-utils/.*
       - zuul.d/gate-utils.yaml