Fix cinder etcd3gw backend_url

Multiple parameters in the URL should be prefixed with an ampersand.

Closes-Bug: #2085908
Change-Id: Ia9e43f7043c0757e11e1924c3df9fe16c037d484
(cherry picked from commit d808d716)

ansible/roles/cinder/templates/cinder.conf.j2

@@ -264,5 +264,5 @@ backend_url = {{ redis_connection_string }}
 # and https://review.opendev.org/466098 for details
 # NOTE(jan.gutter): etcd v3.4 removed the default `v3alpha` api_version. Until
 # tooz defaults to a newer version, we should explicitly specify `v3`
-backend_url = etcd3+{{ internal_protocol }}://{{ kolla_internal_fqdn }}:{{ etcd_client_port }}?api_version=v3{% if openstack_cacert %}?ca_cert={{ openstack_cacert }}{% endif %}
+backend_url = etcd3+{{ internal_protocol }}://{{ kolla_internal_fqdn }}:{{ etcd_client_port }}?api_version=v3{% if openstack_cacert %}&ca_cert={{ openstack_cacert }}{% endif %}
 {% endif %}

releasenotes/notes/fix-cinder-etcd-backend-url-3ca1fa04293c16b5.yaml

+---
+fixes:
+  - |
+    Fixes a bug where the etcd3gw ``backend_url`` in cinder.conf would be
+    invalid when ``openstack_cacert`` was set.
+    `LP#2085908 <https://bugs.launchpad.net/kolla-ansible/+bug/2085908>`__