Fix default values for usage verified event.
Fix default values for usage verified event.

Fix the default values in the compute.instance.verified notification
generated by the UsageHandler. Bandwidth values should be int (0),
not empty string.

Options value should also be '0', not empty string.

Change-Id: I50dc660a46adcd8354e379821e0077cc475e647b

stackforge/stacktach-winchester,openstack/stacktach-winchester