Fix ansible-lint rules tests

ansible-lint does not work when given an empty (/dev/null) config file.

Traceback (most recent call last):
  File "/tmp/ansible.td6htcac/bin/ansible-lint", line 8, in <module>
    sys.exit(main())
  File "/tmp/ansible.td6htcac/lib/python3.6/site-packages/ansiblelint/__main__.py", line 42, in main
    options = cli.get_config(sys.argv[1:])
  File "/tmp/ansible.td6htcac/lib/python3.6/site-packages/ansiblelint/cli.py", line 208, in get_config
    config = load_config(options.config_file)
  File "/tmp/ansible.td6htcac/lib/python3.6/site-packages/ansiblelint/cli.py", line 77, in load_config
    expand_to_normalized_paths(config, config_dir)
  File "/tmp/ansible.td6htcac/lib/python3.6/site-packages/ansiblelint/cli.py", line 40, in expand_to_normalized_paths
    if paths_var not in config:
TypeError: argument of type 'NoneType' is not iterable

Change-Id: Id2a883676c9fbb3a2c704c8cbd8f3cbc28cdc5fb

test-playbooks/ansible-lint-rules/ansible-lint.yaml

@@ -0,0 +1,5 @@
+parseable: true
+quiet: false
+rulesdir:
+  - ../../.rules/
+verbosity: 1

test-playbooks/ansible-lint-rules/run.yaml

@@ -1,6 +1,7 @@
 - hosts: all
   roles:
     - ensure-pip
+    - ensure-virtualenv
   tasks:
     - name: Create tempdir for ansible-lint venv
       tempfile:
@@ -37,7 +38,8 @@
 
     - name: Make sure faulty roles fail linting
       command: >-
-        {{ ansible_lint_tempdir.path }}/bin/ansible-lint -c /dev/null
+        {{ ansible_lint_tempdir.path }}/bin/ansible-lint
+        -c test-playbooks/ansible-lint-rules/ansible-lint.yaml
         -t {{ item | regex_replace('.*/(ZUULJOBS.*?)/.*', '\1') }}
         {{ item }}
       args:
@@ -49,6 +51,7 @@
     - name: Make sure valid roles pass linting
       command: >-
         {{ ansible_lint_tempdir.path }}/bin/ansible-lint
+        -c test-playbooks/ansible-lint-rules/ansible-lint.yaml
         -t {{ item | regex_replace('.*/(ZUULJOBS.*?)/.*', '\1') }}
         {{ item }}
       args: