xci: Create post merge jobs to promote scenarios

xci: Create post merge jobs to promote scenarios

This change lays down the basic job structure for post merge promotion
jobs. The job structure will be

- a top level multijob job that is scenario specific and can not run
concurrently. This job runs distro deploy and test jobs for all the
distros in the first phase concurrently, followed by a common promote job.
- the deploy and test jobs are same as the xci-verify jobs except the
trigger. They are triggered by top level multijob.
- the promote job is run once all the deploy & test phase jobs successfully
completed, uploading promotion metadata to artifacts.opnfv.org.

The builders except set-scenario are left empty in order to try the basic
job setup first. Followup changes will get real things in.

Once the basics are in place, the first promotion will be done using functest
healthcheck and then we will start working on gating scenarios for promotion
using functest smoke and perhaps feature test cases.

Change-Id: Ib91ffe0f3003b86841a62537c52fde176cafa70f
Signed-off-by: Fatih Degirmenci <fdegir@gmail.com>