Added the ability to configured the HTTPServer socket timeout

[dhoard]

Issue

For scenarios where metrics take a long time to retrieve/timeout, we are dependent on the operating system to timeout the socket, resulting in collections getting "stuck"

prometheus/jmx_exporter#911

Proposal

Add a method to HTTPServer.Builder to configure the underline socket timeout for the HTTPServer. Once added, we can expose configuration in the Prometheus JMX Exporter to configure the value.

[dhoard]

Closed with PR #932