Avoid AVD type failing for the new AVD.

Bug: 132216389
Test: m acloud && atest acloud_test --host &&
acloud list
acloud delete
acloud reconnect

Change-Id: If9767aa45165dbfe0ae978373d212656ea21e796
diff --git a/errors.py b/errors.py
index c3c4a71..c9a6f02 100644
--- a/errors.py
+++ b/errors.py
@@ -217,3 +217,7 @@
 
 class ZipImageError(Exception):
     """Zip image error."""
+
+
+class UnknownAvdType(Exception):
+    """Unknow AVD type."""