masakari.conf.j2: render ssl cert/key in [wsgi] section

masakari-api reads ssl_cert_file and ssl_key_file from the [wsgi] config group (CONF.wsgi.ssl_cert_file), not [DEFAULT]. Rendering them under [DEFAULT] alongside use_ssl leaves them empty, so an SSL-enabled masakari-api fails to start with ‘When running server in SSL mode, you must specify both a cert_file and key_file option value in your configuration file’.

Move the cert/key rendering into the [wsgi] section, keeping use_ssl in [DEFAULT] where masakari expects it.