Increased connections to the in_forward plugin server

Hi

We are sending logs from the client to the in_forward input plugin. In
production we the number of connections to the in_forward port increases over
time. This results in huge memory usage on our applications.

In my initial investigation, we think that when keys get expired in [1], the
sender instance on that key doesn't close properly. So when the [2] tried to
recreate the key [2], another connection will be made. Is this a correct
interpretation on what's happening?

[1] https://github.com/fluent/fluent-logger-java/blob/master/src/main/java/org/fluentd/logger/FluentLoggerFactory.java#L36
[2] https://github.com/fluent/fluent-logger-java/blob/master/src/main/java/org/fluentd/logger/FluentLoggerFactory.java#L56