logstash 2.0 doesn't log failure to create new index as a result of mapping error

[purbon]

Moving this from elastic/logstash#4475

there has been a report that if an index request that results in a creation of an index fails due to a mapping conflict with the template no error is logged and logstash discards the event.
this was reported in 2.0 but hasn't been confirmed or checked if fixed in recent 2.x