perf: 修改 applet 是否支持并发，也依赖于 host

apps/terminal/models/applet/applet.py

@@ -194,7 +194,8 @@ class Applet(JMSBaseModel):
         host = self.select_host(user)
         if not host:
             return None
-        can_concurrent = self.can_concurrent or self.type == 'web'
+        host_concurrent = str(host.deploy_options.get('RDS_fSingleSessionPerUser', 0)) == '1'
+        can_concurrent = (self.can_concurrent or self.type == 'web') and host_concurrent
 
         accounts = host.accounts.all().filter(is_active=True, privileged=False)
         private_account = accounts.filter(username='js_{}'.format(user.username)).first()