Follow-up to https://github.com/jenkinsci/remoting/pull/119

> was trying to diagnose a remoting call that bridges two VMs that is hanging. This can be made easier if thread dump allows us to correlate the caller/callee. This change adds the request ID to thread name so that thread dump will show this clearly Also fixes one incorrect use of toString() in diagnosis, which should be getName() — see all the other uses of thread names.