Connect Proxmox VNC sessions through the manager

The vncwebsocket URL used the name of the Proxmox node running the
guest as host. That name often does not resolve on the management
node, and the fingerprint checked is the one of the manager anyway.
Connect to the manager instead, which forwards the websocket to the
right node.

confluent_server/confluent/plugins/hardwaremanagement/proxmox.py

@@ -55,7 +55,9 @@ class KvmConnection:
             'PVEAuthCookie': pac,
             }
         self.protos = ['binary']
-        self.host = host
+        # The manager issued the ticket and owns the pinned fingerprint. It forwards the
+        # websocket to the node running the guest, whose name may not resolve here.
+        self.host = consdata['server']
         self.portnum = 8006
         self.password = consdata['ticket']