(PE-2790) Fix for Jetty always opening binding for a plain http port

Prior to this commit, Jetty would always open a binding for an http
port, whether or not a "port" value was actually specified in the
webserver config for the service.

With the changes in this commit, an http port binding is only
created if one is specified in the webserver config.
Merge pull request #6 from camlow325/feature/master/PE-2790-jetty-always-opens-plain-http-port

(PE-2790) Fix for Jetty always opening binding for a plain http port