Haproxy log formats are escaped by jinja

[Dominik Duranc]

Haproxy template is configured to autoescape special characters like double quotes in custom haproxy log formats, which makes it impossible to use json formatted logs.

Example custom log format:
```
[haproxy_amphora]
user_log_format = '{"project_id":"{{ project_id }}","loadbalancer_id":"{{ lb_id }}","path":"%HP"}'
```

Gets transformed into:
```
[root@amphora-793dc5b2-b718-45ee-940c-61edd82a07e9 ~]# grep log-format /var/lib/octavia/*/haproxy.cfg
    log-format {"project_id":"4c920982974243aeaefc23415c852cec","loadbalancer_id":"08388ef2-734b-4b6d-a8bc-c03975bd7c29""path":"%HP"}
```

This bug can be fixed by adding 'safe' filter to jinja variable:
https://opendev.org/openstack/octavia/src/branch/master/octavia/common/jinja/haproxy/combined_listeners/templates/macros.j2#L194