Only show errors when copying logs

When copying the logs, the log shows all the files copied
which is unnecessary and just consumes console log space.

In this patch we do not show all the files copied, but we
still show errors which is informative enough  without
wasting log lines.

Change-Id: Iffe4baad65d1d2a1812e62f78d54441ae8dbaff2

zuul.d/playbooks/post.yml

@@ -43,6 +43,8 @@
         src: "{{ ansible_user_dir }}/src/{{ zuul.project.canonical_name }}/logs"
         dest: "{{ zuul.executor.log_root }}/"
         mode: pull
+        rsync_opts:
+          - "--quiet"
       when:
         - logs_folder.stat is defined
         - logs_folder.stat.exists | bool