Inconsistent use of Java proxy environment variable vs config

Some plugins utilise a configuration parameter for http communication through a proxy. For example, the Elasticsearch output plugin and http output plugin both utilise the "proxy" config parameters.

They do not respect java environment variables e.g.

export LS_JAVA_OPTS=-Dhttp.proxyHost=localhost

However, other components e.g. the plugin script, seem to respect and utilise this.

Request for behaviour to be standardised.