deploy plugin file to tarballs.o.o/ci/gearman-plugin

This commit will copy the built gearman-plugin.hpi file to
tarballs.o.o with an appended version identifier (i.e.
tarballs.o.o/ci/gearman-plugin/gearman-plugin-${version}.hpi)

Change-Id: Ib0fa29691db27a40507524488588c57760b70776
Reviewed-on: https://review.openstack.org/37139
Reviewed-by: Clark Boylan <clark.boylan@gmail.com>
Approved: Jeremy Stanley <fungi@yuggoth.org>
Reviewed-by: Jeremy Stanley <fungi@yuggoth.org>
Tested-by: Jenkins