[#1978] cli: Add children to the static session on DELETE

If an external session is provided and is not opened by CLI itself, add
children objects to it too. It fixes "not found" errors when removing a big
object with a predefined session (from a file).

Signed-off-by: Pavel Karpy <carpawell@nspcc.ru>

cmd/neofs-cli/modules/object/util.go

@@ -225,6 +225,12 @@ func ReadOrOpenSessionViaClient(cmd *cobra.Command, dst SessionPrm, cli *client.
 	var objs []oid.ID
 	if obj != nil {
 		objs = []oid.ID{*obj}
+
+		if _, ok := dst.(*internal.DeleteObjectPrm); ok {
+			common.PrintVerbose("Collecting relatives of the removal object...")
+
+			objs = append(objs, collectObjectRelatives(cmd, cli, cnr, *obj)...)
+		}
 	}
 
 	finalizeSession(cmd, dst, tok, key, cnr, objs...)