Give zuul user permissions to /opt/wheel/workspace

Otherwise, we cannot write anything to the folder.  Also clean up
shell task since our bash script already setups /bin/bash -ex.

Change-Id: I0a9770dfb1bf252cf092e6edc8491e6d801ab0e3
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

roles/build-wheels/tasks/main.yaml

@@ -4,9 +4,13 @@
 
 - name: Ensure wheel dir exists
   file:
+    group: zuul
+    owner: zuul
     path: "{{ wheel_dir }}"
     state: directory
   become: yes
 
 - name: Build the wheel mirror
-  shell: bash -x scripts/wheel-build.sh {{ wheel_dir }} {{ wheel_python }}
+  shell: ./scripts/wheel-build.sh {{ wheel_dir }} {{ wheel_python }}
+  args:
+    executable: /bin/bash