bin/plugin list show non installed plugins

The `bin/plugin list` command is broken as it shows not installed plugins by default, this makes the user interaction confusing, see the example:

```
skywalker% bin/plugin list
logstash-codec-json
logstash-codec-json_lines
logstash-codec-line
logstash-codec-plain
logstash-filter-clone
logstash-filter-grok
logstash-filter-multiline
logstash-filter-mutate
logstash-input-generator
logstash-input-stdin
logstash-input-tcp
logstash-output-stdout
logstash-patterns-core
skywalker% mvim .
skywalker% bin/plugin uninstall logstash-codec-json
ERROR: Uninstall Aborted, message: This plugin has not been previously installed, aborting
```

I can see the json codec listed, but as is not installed I can not remove it.