Fix server runner helper on JRuby
Fix server runner helper on JRuby

`server.start` starts infinite loop of sockets polling.
On JRuby that leads to thread being constantly in state of `run`.
As socket polling starts immediately, we don't need to wait for
thread actually.

httprb/http,moneyadviceservice/http.rb,httprb/http.rb,davidbegin/http,pezra/http.rb,Connorhd/http.rb