Ignore anonymous request failures checking kv status

When making unauthenticated secret lookup requests, ignore errors that
result from checking the secret mount type.  If it's a persistent error,
the error on the actual lookup.

This restores behavior to before
#1180 .

dependency/vault_common.go

@@ -225,6 +225,12 @@ func isKVv2(client *api.Client, path string) (string, bool, error) {
 			return "", false, nil
 		}
 
+		// anonymous requests may fail to access /sys/internal/ui path
+		// Vault v1.1.3 returns 500 status code but may return 4XX in future
+		if client.Token() == "" {
+			return "", false, nil
+		}
+
 		return "", false, err
 	}