Revert "Report a full_message on a worker crash"

This reverts commit 00f046e.
It was not helpful for an issue I was debugging.

tool/lib/test/unit.rb

@@ -337,7 +337,7 @@ def after_worker_down(worker, e=nil, c=false)
         return unless @options[:parallel]
         return if @interrupt
         flush_job_tokens
-        warn e.full_message if e
+        warn e if e
         real_file = worker.real_file and warn "running file: #{real_file}"
         @need_quit = true
         warn ""