[NetApp] check snapshot presence after creation

Introduce some extra safety by an additional guard.
Losing a snapshot is never an option, this justifies an
additional api call to the NetApp storage back end.

Change-Id: Ibc21b6c72d76a3a804f67e66e7604b3d0be4373f
Related-Bug: #1971710

manila/share/drivers/netapp/dataontap/cluster_mode/lib_base.py

@@ -1750,6 +1750,10 @@ class NetAppCmodeFileStorageLibrary(object):
         snapshot_name = self._get_backend_snapshot_name(snapshot['id'])
         LOG.debug('Creating snapshot %s', snapshot_name)
         vserver_client.create_snapshot(share_name, snapshot_name)
+        if not vserver_client.snapshot_exists(snapshot_name, share_name):
+            raise exception.SnapshotResourceNotFound(
+                name=snapshot_name)
+
         return {'provider_location': snapshot_name}
 
     def revert_to_snapshot(self, context, snapshot, share_server=None):

releasenotes/notes/netapp-check-snapshot-after-creation-1b59038a3a117c65.yaml

@@ -0,0 +1,9 @@
+---
+fixes:
+  - |
+    NetApp driver now checks after sending snapshot-create request that the
+    snapshot has been properly created. If snapshot is not checked, manila
+    assumes that working snapshot is available. But when user tries to access
+    the snapshot, request could fail.
+    `Launchpad bug 1971710 <https://bugs.launchpad.net/manila/+bug/1971710>`_
+    for more details.