fetch-sphinx-tarbal: allow to follow symlinks

Fix bug which prevented find from finding builds when the
folder was a symlink. This can happen if a project using a different
build layout tries to expose the docs at the expected location.

Change-Id: Ib7782b60cef42d2e9fd3077791f06b0f918d7c45

roles/fetch-sphinx-tarball/tasks/main.yaml

@@ -1,6 +1,7 @@
 - name: Inspect sphinx build directory
   find:
     file_type: any
+    follow: true
     paths: "{{ zuul_work_dir }}/{{ sphinx_build_dir }}"
   register: sphinx_dir