list_disk_snapshots.py: look for template snapshots in the chain (#14)

When a VM is created from template with Thin Storage Allocation,
the parent of one of the snapshots will be the template image, thus
not returned in the result set for the list disksnapshots request.
In this case, when requesting snapshots of a disk created this way -
this script returns an error.

This patch takes advantage of the disks/xxx/disksnapshots API with
'include_active' and 'include_template' flags to fetch all the
snapshots required for the chain reconstruction

Bug-Url: https://bugzilla.redhat.com/1900597

Author: mkemel

examples/list_disk_snapshots.py

@@ -45,28 +45,13 @@ def parse_args():
     # Find the disk.
     disks_service = connection.system_service().disks_service()
     disk_service = disks_service.disk_service(args.disk_id)
-
-    try:
-        disk = disk_service.get()
-    except sdk.NotFoundError:
-        raise RuntimeError("No such disk: {}".format(args.disk_id)) from None
-
-    # Find the storage domain service.
-    sd_id = disk.storage_domains[0].id
-    sds_service = connection.system_service().storage_domains_service()
-    sd_service = sds_service.storage_domain_service(sd_id)
-
-    # Find the disk snapshots using the disk snapshots service.
-    # TODO: Use disk's snapshots service to get filter the snapshot on the
-    # server side.
-    disk_snapshots_service = sd_service.disk_snapshots_service()
+    disk_snapshots_service = disk_service.disk_snapshots_service()
 
     # Create mapping from snapshot parent to snapshot, used to reconstruct the
     # snapshot chain.
     snapshots = {}
-    for s in disk_snapshots_service.list(include_active=True):
-        if s.disk.id != disk.id:
-            continue
+
+    for s in disk_snapshots_service.list(include_active=True, include_template=True):
         parent = s.parent.id if s.parent else None
         child = {
             "actual_size": s.actual_size,