Install kubectl via openshift client tools

Instead of installing kubectl with snaps, which seem to be laky
in tests, just download the oc client tools tarball and unpack it.
This is how we get kubectl for the zuul images and it seems to
work nicely there.

Change-Id: I79590a2eeaf32722d231c2bfec35d264696b7e7a

playbooks/roles/install-kubectl/defaults/main.yaml

@@ -0,0 +1,2 @@
+kubectl_openshift_url: https://github.com/openshift/origin/releases/download/v3.11.0/openshift-origin-client-tools-v3.11.0-0cbc58b-linux-64bit.tar.gz
+kubectl_openshift_checksum: sha256:4b0f07428ba854174c58d2e38287e5402964c9a9355f6c359d1242efd0990da3

playbooks/roles/install-kubectl/tasks/main.yaml

@@ -1,16 +1,32 @@
 - name: Install snapd
   package:
     name: snapd
-    state: present
+    state: absent
 
-- name: Install kubectl
-  command: snap install kubectl --classic
-
-# /snap/bin is often in the path, but not in a non-login shell, which
-# makes it difficult to use via ansible.  Add an extra symlink so we
-# can always find it.
-- name: Symlink snapd into /usr/local/bin
+- name: Make /opt/oc directory
   file:
-    src: /snap/bin/kubectl
-    dest: /usr/local/bin/kubectl
-    state: link
+    path: /opt/oc
+    state: directory
+
+- name: Download openshift client tarball
+  get_url:
+    url: "{{ kubectl_openshift_url }}"
+    checksum: "{{ kubectl_openshift_checksum }}"
+    dest: /opt/oc.tgz
+
+- name: Extract openshift client tarball
+  unarchive:
+    src: /opt/oc.tgz
+    dest: /opt/oc
+    extra_opts:
+      - --strip-components=1
+
+- name: Copy files into /usr/local
+  copy:
+    remote_src: true
+    src: "/opt/oc/{{ item }}"
+    dest: "/usr/local/bin/{{ item }}"
+    mode: 0755
+  loop:
+    - oc
+    - kubectl