set owner and group to no for fetch-devstack-log-dir

As the user on the node under test may not exist on
the zuul executor node we do not copy the log owner
or group to avoid the rsync task failing when it
tries to chown the files.

Change-Id: I500cf3692a4d27b0c2a0a4f5586580d180a8778e

roles/fetch-devstack-log-dir/tasks/main.yaml

@@ -1,5 +1,10 @@
+# as the user in the guest may not exist on the executor
+# we do not preserve the group or owner of the copied logs.
+
 - name: Collect devstack logs
   synchronize:
     dest: "{{ zuul.executor.log_root }}/{{ inventory_hostname }}"
     mode: pull
     src: "{{ devstack_base_dir }}/logs"
+    group: no
+    owner: no