add-bastion-host: use hostname directly

Similar to I84acaa917187db092a302519c14bc94a6a87c2c0, this is a
follow-on to I286796ebd71173019a627f8fe8d9a25d0bfc575a.

At this point, there is no "bastion" group for the executor Ansible to
use.

The idea here is to reduce the number of places we're directly
referencing bridge.openstack.org.  We could move this into a job
variable, but that's the same as defining it here.  KISS and reference
it directly here (since it's in a role and used multiple times, it's
still better than hardcoding in multiple places).

Change-Id: If6dbcb34e25e3eb721cd2892b8adb84344289882

playbooks/zuul/roles/add-bastion-host/tasks/main.yaml

@@ -1,21 +1,13 @@
-- name: Get the bastion hostname
-  set_fact:
-    _bastion_hostname: '{{ groups["bastion"][0] }}'
-
-- name: Show bastion details
-  debug:
-    msg: "Bastion host is {{ _bastion_hostname }}"
-
-- name: Add bastion host to inventory for playbook
+- name: Add bastion host to inventory for production playbook
   add_host:
-    name: '{{ _bastion_hostname }}'
+    name: 'bridge.openstack.org'
     groups: 'bastion'
     ansible_python_interpreter: python3
     ansible_user: zuul
     # Without setting ansible_host directly, mirror-workspace-git-repos
     # gets sad because if delegate_to localhost and with add_host that
     # ends up with ansible_host being localhost.
-    ansible_host: '{{ _bastion_hostname }}'
+    ansible_host: 'bridge.openstack.org'
     ansible_port: 22
     # Port 19885 is firewalled
     zuul_console_disabled: true