bridge-bootstrap: pass hostname for testing

This is another fixup for Iebaeed5028050d890ab541818f405978afd60124

As described inline; in production we want the nested ansible to use
the production inventory; but in the gate we haven't yet built the
inventory used for testing.  Pass an inventory list there.

Change-Id: If09ecb873368621687f6e396f766f4e22635c188

playbooks/bootstrap-bridge.yaml

@@ -62,10 +62,17 @@
 
     - name: Install root key
       shell: >-
-          ansible-playbook -v ${ROOT_RSA_KEY} -i "localhost,"
+          ansible-playbook -v ${ROOT_RSA_KEY} ${BRIDGE_INVENTORY}
           /home/zuul/src/opendev.org/opendev/system-config/playbooks/zuul/run-production-bootstrap-bridge-add-rootkey.yaml
           > /var/log/ansible/install-root-key.{{ lookup('pipe', 'date +%Y-%m-%dT%H:%M:%S') }}.log 2>&1
       environment:
         ROOT_RSA_KEY: '{{ "-e @/home/zuul/root-rsa-key.json" if root_rsa_key is defined else "" }}'
+        # In production "install-ansible" has setup ansible to point
+        # to the system-config inventory which has bridge in it.  In
+        # the gate, bridge is ephemeral and we haven't yet built the
+        # inventory to use for testing (that is done in
+        # zuul/run-base.yaml).  Pass the hostname -- the playbook uses
+        # the local connection.
+        BRIDGE_INVENTORY: '{{ "-ibridge.openstack.org," if root_rsa_key is defined else "" }}'
         ANSIBLE_ROLES_PATH: '/home/zuul/src/opendev.org/opendev/system-config/playbooks/roles'
       no_log: true