Fix lookup of subunit files in fetch-subunit-output

The role allows override of the zuul_work_dir variable, however in the
step where it retrieves the test results is the only step where it
prepends the directory with a fixed path. This breaks the step if the
zuul_work_dir given is a fully qualified path.

This patch defaults the zuul_work_dir to a fully qualified directory and
standarizes the usage zuul_work_dir across the role.

Change-Id: I62bc7571f625586a0d1b660f896e0c7cbaeae6e1

roles/fetch-subunit-output/README.rst

@@ -3,9 +3,9 @@ Collect subunit outputs
 **Role Variables**
 
 .. zuul:rolevar:: zuul_work_dir
-   :default: {{ zuul.project.src_dir }}
+   :default: {{ ansible_user_dir }}/{{ zuul.project.src_dir }}
 
-   Directory to work in
+   Directory to work in. It has to be a fully qualified path.
 
 .. zuul:rolevar:: tox_envlist
 

roles/fetch-subunit-output/defaults/main.yaml

@@ -1,3 +1,3 @@
 ---
 tox_envlist: ""
-zuul_work_dir: "{{ zuul.project.src_dir }}"
+zuul_work_dir: "{{ ansible_user_dir }}/{{ zuul.project.src_dir }}"

roles/fetch-subunit-output/tasks/process.yaml

@@ -10,7 +10,7 @@
 - name: Find subunit files
   find:
     paths:
-      - "{{ ansible_user_dir }}/{{ zuul_work_dir }}"
+      - "{{ zuul_work_dir }}"
     patterns:
       - testr_results.html
       - testrepository.subunit