Improve error handling when a network is removed while having a XO backup network set

[olivierlambert]

If you remove a network (eg you remove a PIF and/or a network) while having a XO backup network set on this network, any backup from XO will fail with something like that:

 "result": {
        "code": "UUID_INVALID",
        "params": [
          "network",
          "53f8ab42-ec1e-f5c1-a5b7-cf39b7a42fc3"
        ],
        "call": {
          "method": "network.get_by_uuid",
          "params": [
            "53f8ab42-ec1e-f5c1-a5b7-cf39b7a42fc3"
          ]
        },
        "message": "UUID_INVALID(network, 53f8ab42-ec1e-f5c1-a5b7-cf39b7a42fc3)",
        "name": "XapiError",
        "stack": "XapiError: UUID_INVALID(network, 53f8ab42-ec1e-f5c1-a5b7-cf39b7a42fc3)\n    at XapiError.wrap (file:///home/anthony/xen-orchestra/packages/xen-api/_XapiError.mjs:16:12)\n    at file:///home/anthony/xen-orchestra/packages/xen-api/transports/json-rpc.mjs:38:21\n    at process.processTicksAndRejections (node:internal/process/task_queues:95:5)"
      }

It's not trivial to find it's because of that. It would be great to catch this error and either explain the issue (change your backup network set on your pool or remove it) or remove automatically the XO backup network on this pool.

Source: multiple threads on the forum, last one https://xcp-ng.org/forum/topic/9593/error-uuid_invalid-network-cannot-backup-any-vm