bring back the thread wrapper around jetty start/stop so we can wait for the server to stop fully.
notes and refined logging
use ISE
Merge branch 'NEXUS-6027-simplify-jetty-integration' into NEXUS-6027-remove-appcontext

Conflicts:
	components/nexus-bootstrap/src/main/java/org/sonatype/nexus/bootstrap/jetty/JettyServer.java