Fix expected error details from jsonschema
Fix expected error details from jsonschema

The jsonschema 2.4.0 release slightly changed some of the error messages
that are provided when validation fails. This updates the unit tests to
expect the proper string and avoid failing as a result.

Change-Id: Ic8e32140e49e394659e7ebbecb28afb704b23b7c
Closes-bug: #1358881

luogangyi/bcec-nova,luogangyi/bcec-nova,leilihh/nova,leilihh/nova,leilihh/novaha,leilihh/novaha