When "Take Snapshot" is enabled on a Cloud Sync Task and a Zvol exists everywhere on the system the sync task fails with "KeyError: 'mountpoint'".

The error is caused by this check in the cloud_sync middleware: https://github.com/truenas/middleware/blob/bc97adfdcaec5da97c9f2e408908259c154f536a/src/middlewared/middlewared/plugins/cloud_sync.py#L468

The mountpoint proptery doesn't exist on the Zvol and the check fails.

Full error:

Error: Traceback (most recent call last):
File "/usr/lib/python3/dist-packages/middlewared/job.py", line 409, in run
await self.future
File "/usr/lib/python3/dist-packages/middlewared/job.py", line 445, in __run_body
rv = await self.method(*([self] + args))
File "/usr/lib/python3/dist-packages/middlewared/schema.py", line 1269, in nf
return await func(*args, **kwargs)
File "/usr/lib/python3/dist-packages/middlewared/plugins/cloud_sync.py", line 1103, in sync
await self._sync(cloud_sync, options, job)
File "/usr/lib/python3/dist-packages/middlewared/plugins/cloud_sync.py", line 1150, in _sync
await rclone(self.middleware, job, cloud_sync, options["dry_run"])
File "/usr/lib/python3/dist-packages/middlewared/plugins/cloud_sync.py", line 191, in rclone
dataset, recursive = get_dataset_recursive(
File "/usr/lib/python3/dist-packages/middlewared/plugins/cloud_sync.py", line 462, in get_dataset_recursive
datasets = [
File "/usr/lib/python3/dist-packages/middlewared/plugins/cloud_sync.py", line 468, in <listcomp>
if dataset["properties"]["mountpoint"]["value"] != "none"
KeyError: 'mountpoint'