fetch-tox-output: remove --ignore-missing-args

This is no longer needed since the task errors are now ignored.
Moreover this option doesn't work on el7.

Change-Id: Ic6b32999eef2fa26d63ed5d34b3b05b3ade60b32

roles/fetch-tox-output/tasks/main.yaml

@@ -37,8 +37,6 @@
     mode: pull
     src: "{{ zuul_work_dir }}/.tox/{{ item }}/log/"
     verify_host: true
-    rsync_opts:
-      - "--ignore-missing-args"
   with_items: "{{ envlist }}"
   # some tox runs may not create a virtualenv and thus have
   # no ./tox/env directory