Describe the bug

Data reported by to OTEL service in Jaeger format might get duplicated tag span.kind=server. The tag is probably duplicated during the model conversion.

To Reproduce
Steps to reproduce the behavior:

1. docker run -it --rm -e "ES_JAVA_OPTS=-Xms2g -Xmx2g" -p 9200:9200 -p 9300:9300 -e "http.host=0.0.0.0" -e "discovery.type=single-node" --name=elasticsearch docker.elastic.co/elasticsearch/elasticsearch-oss:6.8.4
2. SPAN_STORAGE_TYPE=elasticsearch go run -tags ui ./cmd/all-in-one/main.go --new-metrics=true (after PR Add native OTEL ES exporter #2295)
3. open Jaeger UI and create some requests. The first span from traces reported by query service has a warning Duplicate tag "span.kind:server"

Expected behavior

A single span kind tag