Telgraf Helm Chart does create Service config for snmp_trap plugin

When the input plugin `snmp_trap` is used the helm chart does not render a service.

This is due to the fact that there is no special treatment defined for itin the service template, beginning from l22:

https://github.com/influxdata/helm-charts/blob/fe0d58beab2c0c164e355499483a898d1cf08a24/charts/telegraf/templates/service.yaml#L22-L93

The result is that while telegraf listens on the SNMP traps within the pod, the listener is not accessible from the outside.

Start in charts/telegraf/templates/service.yaml around lines 22-93, where the issue reports that snmp_trap receives no special treatment. Render the Telegraf chart with the snmp_trap input enabled and inspect the generated Service. Done means the rendered Service exposes the SNMP trap listener so it is reachable from outside the pod.

Written by the indexing model from the issue text.