Bugfix to HystrixBadRequestException handling

Logs were spuriously getting generated by `HystrixBadRequestException`s.

Only functional diff is that the `log.warn` is now not called unless the `HystrixCommandExecutionHook.onRunError` invocation throws an Exception.  I didn't add a mockLogger for testing purposes, but checked that the `HystrixBadRequestException` case was completely handled already - so no regressions here.

Also, changed the log message to match the `HystrixCommandExecutionHook` method name : `onRunError`