Faster server shutdown

Since recently (but cannot remember if it is since HF11 or 12), most of our (resales) serves can't stop properly. We almost always have:

 ./nuxeoctl stop
Stopping server...............................................................No answer from server, try to kill process 5477...
Server forcibly stopped.
 

This happens in "complex" servers (complex means with a lot of plugins, with Arender, etc.) but also on Mac localhost with basic plugins installed (webUI, spreadsheet and a couple others)

In attachments, please find some files, result of  jcmd Bootstrap Thread.print > /tmp/thread-dump-$(date +'%Y-%m-%dT%H-%M-%S').txt