Parse Jenkins' log timestamps with logstash.

* modules/openstack_project/templates/logstash/agent.conf.erb: Use the
grok, date, and mutate filters to transform Jenkins' logs from
"2013-04-08 22:46:43.659 | Started by user OpenStack Hudson" to

  @timestamp: 2013-04-08 22:46:43.659
  @message: Started by user OpenStack Hudson

Change-Id: I6aac49b4717f25838c13a2563360d03e40bb19e3
Reviewed-on: https://review.openstack.org/26446
Approved: Clark Boylan <clark.boylan@gmail.com>
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins