Fix logstash gearman puppet.

* modules/openstack_project/manifests/logstash.pp: Concat is not
available in our version of puppetlabs stdlib. Use flatten instead
which is available. Remove dependency on non existant logstash::indexer
class. Fix requires orders.

* modules/openstack_project/manifests/logstash_worker.pp: Fix requires
orders.

* modules/openstack_project/files/logstash/jenkins-log-client.init
* modules/openstack_project/files/logstash/jenkins-log-worker.init:
Set pidfile argument when calling scripts.

* modules/openstack_project/files/logstash/log-gearman-worker.py:
Use python2 compatible gzip.GzipFile instead of gzip.decompress. Send
work exception instead of work fail when an exception happens. Log these
exceptions locally as well.

Change-Id: Idf0a873215acb72187e058a0306a21ccd928d464
Reviewed-on: https://review.openstack.org/32804
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Khai Do <zaro0508@gmail.com>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Clark Boylan <clark.boylan@gmail.com>
Tested-by: Jenkins