Fix setup httpProxy property

[wmellouli]

Issue description

We cannot disable the use of system Http proxy properties (http.proxyHost and http.proxyPort) using the property es.net.proxy.http.use.system.props. As a workaround, we have to use the https property es.net.proxy.https.use.system.props.

In line 410 of class org.elasticsearch.hadoop.cfg.Settings, we load HTTPS properties instead of HTTP properties:
org.elasticsearch.hadoop.cfg.Settings#Line410

See also: org.elasticsearch.hadoop.rest.commonshttp.CommonsHttpTransport#Line264

Steps to reproduce

Set an http proxy in your system, and then try to disable the use of system Http proxy properties:

es.net.proxy.http.use.system.props = false

this property should not have an effect.

As a workaround, when you use the https property instead:

es.net.proxy.https.use.system.props = false

now, it should work.

[jbaiera]

Thanks for opening a PR @wmellouli, but could you update the post with a synopsis for the changes?

[wmellouli]

@jbaiera I added the Issue description and steps to reproduce

[jbaiera]

@wmellouli Awesome, thanks. The change looks good to me. Good find.