This commit refactors 'event_status' view and adds
'BillingSession.get_event_status' method.
This refactoring will help in minimizing duplicate code
while supporting both realm and remote_server customers.
Adds request as a parameter to json_success as a refactor towards
making `ignored_parameters_unsupported` functionality available
for all API endpoints.
Also, removes any data parameters that are an empty dict or
a dict with the generic success response values.