[mq] Allow for rabbit kombu ssl configuration

As defined in oslo.messaging for rabbit: https://github.com/openstack/oslo.messaging/blob/02ab25ecc61d539ddceef9e2a05ee03601f70682/oslo_messaging/_drivers/impl_rabbit.py#L55

cfg.StrOpt('kombu_ssl_keyfile',
               default='',
               deprecated_group='DEFAULT',
               help='SSL key file (valid only if SSL enabled).'),
    cfg.StrOpt('kombu_ssl_certfile',
               default='',
               deprecated_group='DEFAULT',
               help='SSL cert file (valid only if SSL enabled).'),
    cfg.StrOpt('kombu_ssl_ca_certs',
               default='',
               deprecated_group='DEFAULT',
               help='SSL certification authority file '
                    '(valid only if SSL enabled).'),
    cfg.FloatOpt('kombu_reconnect_delay',
                 default=1.0,
                 deprecated_group='DEFAULT',
                 help='How long to wait before reconnecting in response to an '
                      'AMQP consumer cancel notification.'),
    cfg.IntOpt('kombu_reconnect_timeout',
               # NOTE(dhellmann): We want this to be similar to
               # rpc_response_timeout, but we can't use
               # "$rpc_response_timeout" as a default because that
               # option may not have been defined by the time this
               # option is accessed. Instead, document the intent in
               # the help text for this option and provide a separate
               # literal default value.
               default=60,
               help='How long to wait before considering a reconnect '
                    'attempt to have failed. This value should not be '
                    'longer than rpc_response_timeout.'),