Listener died (Gelf) - logstash 2.3.2

Hi,

I have a logstash collector with input in gelf and output Redis.

Sometimes the listener died :

```
{:timestamp=>"2016-07-26T22:00:56.628000+0200", :message=>"gelf listener died", :exception=>#:warn
```

I want to upgrade logstash-input-gelf plugin to try if it fix the previous error but I have another error :

```
/opt/logstash/bin/plugin update logstash-input-gelf
The use of bin/plugin is deprecated and will be removed in a feature release. Please use bin/logstash-plugin.
You are updating logstash-input-gelf to a new version 3.0.2, which may not be compatible with 2.0.7. are you sure you want to proceed (Y/N)?

Y
No plugin updated
```

Centos 6.7
Logstash 2.3.2
logstash-input-gelf 2.0.7
Redis 3.0.7

My configuration :

```
input {
gelf {
type => "gelf"
port => "12201"
}
}

output {
redis {
host => "127.0.0.1"
data_type => "list"
key => "logstash"
}
}
```

Start with logstash-input-gelf/lib/logstash/inputs/gelf.rb, especially new_event at line 130 and the udp_listener path at line 113. Reproduce the listener failure with the reported Logstash 2.3.2 and plugin 2.0.7 configuration, then verify the listener no longer dies and that the plugin update path is compatible.

Written by the indexing model from the issue text.