Standardise ownership of *_venv_bin directories

This review standardises the ownership of the *_venv_dir directories by
ensuring all are created as root instead of using the service's user.
This behaviour already exists in the following roles:

- os_aodh
- os_glance
- os_swift

Change-Id: Idab42b83bece3624271780105f6a937eb88c7491

tasks/horizon_pre_install.yml

@@ -50,10 +50,8 @@
   file:
     path: "{{ item.path }}"
     state: directory
-    owner: "{{ item.owner|default(horizon_system_user_name) }}"
-    group: "{{ item.group|default(horizon_system_group_name) }}"
   with_items:
-    - { path: "/openstack/venvs", mode: "0755", owner: "root", group: "root" }
+    - { path: "/openstack/venvs" }
     - { path: "{{ horizon_venv_bin }}" }
   when: horizon_venv_enabled | bool
   tags: