Add post job to publish build artifact to tarball.o.o

This commit adds a post job to deploy the gearman-plugin
artifact (gearman-plugin.hpi) to tarball.o.o

.gitignore
   ignore auto generated eclipse project file

modules/openstack_project/files/jenkins_job_builder/config/gearman-plugin.yaml
   the new gearman-plugin-tarball job (copied from gerrit.yaml)

modules/openstack_project/files/zuul/layout.yaml
   hook job into build system

Change-Id: I59d9e3b446646fd879d827fd0aeb35356865f4d0
Reviewed-on: https://review.openstack.org/24663
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: James E. Blair <corvus@inaugust.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins