[Build] Allow graceful shutdown of Jetty
[Build] Allow graceful shutdown of Jetty

* Introduced stopWait timeout for maven-jetty-plugin in order
  to improve test stability. If the entry is omitted, no wait
  is done, so that if shutdown takes too long, another jetty
  could get started potentially leading to 'address already
  in use' errors.

* The wait ends as soon as jetty has stopped or when the
  timeout has been reached.

Change-Id: I25ede0a40b1bcaa12616100b1c7097c8988c88f2

bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,clive-jevons/joynr,bmwcarit/joynr,bmwcarit/joynr,clive-jevons/joynr