Add grenade logs to logstash.

Add grenade new/ and old/ logs to logstash. To do this without tripling
HTTP GETs for every finished job add a job filter to the log gearman
client that when present only attempts to grab files if the job name
matches the job filter.

Change-Id: Ia33722bf71d482f2fd6b655b28090a10bf46af54
Merge "Add grenade logs to logstash."