Avoid potential loop variable collision in base-test post-logs

Make the variable different from 'item' to avoid any possible
collision with other uses of that name from ansible loops.

Change-Id: I6dfb6f8494538acfdfa4f3f93e02cb955fd2bd9c

playbooks/base-test/post-logs.yaml

@@ -10,13 +10,15 @@
         local_log_download_api: 'https://zuul.opendev.org/api/tenant/{{ zuul.tenant }}'
     - name: Select random swift provider for logs upload
       set_fact:
-        _swift_provider_name: "{{ item }}"
+        _swift_provider_name: "{{ opendev_base_item }}"
       with_random_choice:
         - 'ovh_bhs'
         - 'ovh_gra'
         - 'rax_dfw'
         - 'rax_iad'
         - 'rax_ord'
+      loop_control:
+        loop_var: 'opendev_base_item'
     - name: Upload swift logs to {{ _swift_provider_name }}
       no_log: true
       include_role: