[REST] Simultaneous call to stop don't stop the servers

This was observed in a cluster of 3 servers in the same machine, listening on ports 11222, 11322, 11422. A script would call stop on each of the server individually:

http://localhost:11222/rest/v2/server?action=stop
http://localhost:11322/rest/v2/server?action=stop
http://localhost:11422/rest/v2/server?action=stop

All the commands return code 200 but the servers are not stopped, the processes are still alive.

This is a regression from 10.0.0.CR3 where those ops were working correctly.