Delete error volumes when deleting instance

Backport candidate.

Change-Id: I799f7b30e1af396a8ae540cff2ba8b548a23f82c
Story: 2007436
Task: 39083

trove/instance/models.py

@@ -789,7 +789,9 @@ class BaseInstance(SimpleInstance):
         try:
             if self.volume_id:
                 volume = self.volume_client.volumes.get(self.volume_id)
-                if volume.status == "available":
+                if volume.status in ["available", "error"]:
+                    LOG.info("Deleting volume %s for instance %s",
+                             self.volume_id, self.id)
                     volume.delete()
         except Exception as e:
             LOG.warning("Failed to delete volume for instance %s, error: %s",