Catch SIGTERM, SIGINT, SIGHUP and SIGQUIT to properly shutdown the

server.

tests/conftest.py

@@ -15,5 +15,5 @@ def server(request):
     server_script = os.path.join(cwd, "../gns3server/main.py")
     process = subprocess.Popen([sys.executable, server_script, "--port=8000"])
     time.sleep(0.1)  # give some time for the process to start
-    request.addfinalizer(process.kill)
+    request.addfinalizer(process.terminate)
     return process