imapc: Remove root_sep_lookup_failed cache

The auth_failed_* should already be enough for this. This removal also
fixes the storage error message to be auth_failed_reason when possible.

src/lib-storage/index/imapc/imapc-list.c

@@ -329,12 +329,9 @@ static char imapc_list_get_hierarchy_sep(struct mailbox_list *_list)
 	struct imapc_mailbox_list *list = (struct imapc_mailbox_list *)_list;
 	char sep;
 
-	if (list->root_sep_lookup_failed ||
-	    imapc_list_try_get_root_sep(list, &sep) < 0) {
+	if (imapc_list_try_get_root_sep(list, &sep) < 0) {
 		/* we can't really return a failure here. just return a common
 		   separator and fail all the future list operations. */
-		list->root_sep_lookup_failed = TRUE;
-		mailbox_list_set_internal_error(_list);
 		return '/';
 	}
 	return sep;
@@ -551,13 +548,10 @@ static int imapc_list_refresh(struct imapc_mailbox_list *list)
 	struct imapc_simple_context ctx;
 	struct mailbox_node *node;
 	const char *pattern;
+	char sep;
 
-	if (imapc_storage_client_handle_auth_failure(list->client))
-		return -1;
-	if (list->root_sep_lookup_failed) {
-		mailbox_list_set_internal_error(&list->list);
+	if (imapc_list_try_get_root_sep(list, &sep) < 0)
 		return -1;
-	}
 	if (list->refreshed_mailboxes)
 		return 0;
 
@@ -783,14 +777,12 @@ imapc_list_subscriptions_refresh(struct mailbox_list *_src_list,
 	struct imapc_simple_context ctx;
 	struct imapc_command *cmd;
 	const char *pattern;
-	char dest_sep = mail_namespace_get_sep(dest_list->ns);
+	char list_sep, dest_sep = mail_namespace_get_sep(dest_list->ns);
 
 	i_assert(src_list->tmp_subscriptions == NULL);
 
-	if (src_list->root_sep_lookup_failed) {
-		mailbox_list_set_internal_error(_src_list);
+	if (imapc_list_try_get_root_sep(src_list, &list_sep) < 0)
 		return -1;
-	}
 
 	if (src_list->refreshed_subscriptions) {
 		if (dest_list->subscriptions == NULL)