fluentd-ui start fail

This is my config info:

```
[root@Jasontom ~]# td-agent --version
td-agent 1.9.0

[root@Jasontom ~]# td-agent-gem --version
WARN: Unresolved specs during Gem::Specification.reset:
tzinfo (< 3.0, >= 1.0, >= 1.0.0)
WARN: Clearing out unresolved specs.
Please report a bug if this causes problems.
2.6.14

[root@Jasontom ~]# td-agent-gem install -V fluentd-ui
.....
.....

[root@Jasontom ~]# /opt/td-agent/embedded/lib/ruby/gems/2.4.0/bin/fluentd-ui setup
[root@Jasontom ~]# /opt/td-agent/embedded/lib/ruby/gems/2.4.0/bin/fluentd-ui start
[root@Jasontom ~]# /opt/td-agent/embedded/lib/ruby/gems/2.4.0/bin/fluentd-ui status
fluentd-ui is stopped
```

Execute start without any output.