Don't install a blank docker daemon config

It's not necessary to install an empty config file, and doing so
will prevent us from using other roles to configure mirrors on
test hosts.

Change-Id: I3d7eb615f1e297fde2d693b5fc64bc6e691e2c22

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

@@ -4,15 +4,6 @@
     state: directory
     path: /etc/docker
 
-- name: Install docker configuration
-  become: yes
-  template:
-    dest: /etc/docker/daemon.json
-    group: root
-    mode: 0644
-    owner: root
-    src: daemon.json.j2
-
 - name: Install docker-ce from upstream
   include: upstream.yaml
   when: use_upstream_docker

playbooks/roles/install-docker/templates/daemon.json.j2

@@ -1,2 +0,0 @@
-{
-}

testinfra/test_docker.py

@@ -16,11 +16,6 @@
 testinfra_hosts = ['bionic-docker']
 
 
-def test_docker_config(host):
-    daemon_json = host.file('/etc/docker/daemon.json')
-    assert daemon_json.exists
-
-
 def test_docker_service(host):
     docker = host.service('docker')
     assert docker.is_running