Allow puppetmaster to send reports to logstash

Add a Puppet report handler for sending data to logstash. Each report is
converted to a single log event which is sent as newline delimited json
to Logstash over a tcp transport.

On the Logstash side, the event's "host" field is fixed to contain the
hostname of the Puppet agent that originated the report rather than the
ip address of the Puppetmaster and tags for indexing in ElasticSearch.

This results in the full diff of the Puppet run being stored in
Logstash. As such, care should be taken in ensuring that the target
logstash cluster is properly secured for types of sensitive data that
this may reveal.

Bug: 60690
Change-Id: I604582a7faf902ba899985ca7127b95de1fa9b20