Improve output of Verify Sphinx build task

Avoid repeated output of HTML content on console and
marks the task as not changed in ansible.

A grep failure would be easy to investigate as the file is collected.

Change-Id: I7520e8f3b5c01f39affeac398aeaeffe6dfdb6cf
Partial-Bug: #1787912

roles/collect-logs/tasks/main.yml

@@ -21,8 +21,10 @@
     - not artcl_collect|bool
 
 - name: Verify Sphinx build
-  shell: grep "{{ item }}" "{{ artcl_collect_dir }}/docs/build/index.html"
+  shell:
+    grep -q "{{ item }}" "{{ artcl_collect_dir }}/docs/build/index.html"
   with_items: "{{ artcl_create_docs_payload.table_of_contents }}"
+  changed_when: false
   when:
     - artcl_gen_docs|bool
     - artcl_verify_sphinx_build|bool