Make sure /etc/hostname is valid for SELinux

In the gate, it is possible for /etc/hostname to not have a valid
SELinux security conext. So, reset them to default before we update
the hostname to avoid:

  TASK: [Assign hostname]
  failed: [node1] => {"failed": true}
  msg: Command failed rc=1, out=, err=Could not set property: Access
  denied

Closes-Bug: #1568047
Change-Id: Ie30c8437b310d1ea5bc75307375c255131dfe934
Needed-By: I2ff5fbb315832b8cf07c93d0dd0cdaacd958631e

tools/setup_nodes.yml

@@ -7,6 +7,10 @@
       src: /etc/hosts
       dest: /etc/hosts
 
+  - name: Ensure /etc/hostname is valid for SELinux
+    command: restorecon -v /etc/hostname
+    when: ansible_os_family == 'RedHat'
+
   - name: Assign hostname
     hostname:
       name: "{{ inventory_hostname }}"