Avoid using 'foo' as invalid JSON test data
Avoid using 'foo' as invalid JSON test data

Downstream test environments appear to have a file called 'foo' either
created out-of-band, or created by tests executed in a
non-deterministic order.

This changes the test data to very invalid json which is unlikely to
be a filename, ensuring the expected codepath is tested.

Change-Id: I88ed81337c6e2d724b3cf4ddf90e0d60fa052d1c

openstack/python-ironicclient,openstack/python-ironicclient