Dashboard not starting with custom certs.

[dopry]

#136 fixed the configuration being picked up, but I am still having issues with custom certs from letsencrypt. They same certs are working for mqtts/wss and were working with 2.x, but with v3.2.3 the dashboard won't start. I

dashboard.listener.https.certfile=/certs/live/{{removed to protect the innocent}}/fullchain.pem
dashboard.listener.https.keyfile=/certs/live/{{removed to protect the innocent}}/privkey.pem

2019-09-16 17:56:27.535 [error] [Plugins] Load plugin emqx_dashboard failed, cannot start plugin emqx_dashboard for {bad_return,
                                                                                      {{emqx_dashboard_app,
                                                                                        start,
                                                                                        [normal,
                                                                                         []]},
                                                                                       {'EXIT',
                                                                                        {{badmatch,
                                                                                          {error,
                                                                                           {{shutdown,
                                                                                             {failed_to_start_child,
                                                                                              ranch_acceptors_sup,
                                                                                              {listen_error,
                                                                                               'https:dashboard',
                                                                                               {options,
                                                                                                {ciphers,
                                                                                                 ["ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-SHA384:ECDHE-RSA-AES256-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256"]}}}}},