Add test_setup_skip role variable

This allows jobs which inherit from unittests to specify that
the test-setup script should not be run.  Some "unit test" jobs
are simple enough that they do not need to perform costly setup
for a full test run.

Change-Id: I5826bed411c42f9b3e0477b351bd82bd964d2fac

roles/test-setup/README.rst

@@ -20,6 +20,12 @@ automated testing system and developers.
    String of optional command line options passed to
    the test-setup script.
 
+.. zuul:rolevar:: test_setup_skip
+   :default: false
+
+   Set this to true to skip running the test-setup script even if it
+   exists.
+
 .. zuul:rolevar:: zuul_work_dir
    :default: {{ zuul.project.src_dir }}
 

roles/test-setup/defaults/main.yaml

@@ -1,6 +1,6 @@
 ---
 test_setup_args: ""
 test_setup_environment: {}
+test_setup_skip: false
 
 zuul_work_dir: "src/{{ zuul.project.canonical_name }}"
-

roles/test-setup/tasks/main.yaml

@@ -1,4 +1,4 @@
-- name: Check if project's tools/test-setup.sh exists
+- name: "Check if project's tools/test-setup.sh exists"
   stat:
     path: "{{ zuul_work_dir }}/tools/test-setup.sh"
   register: p
@@ -11,3 +11,4 @@
   when:
     - p.stat.exists
     - p.stat.executable
+    - not test_setup_skip