Run gerrit pipeline on github PR

When to do it:

You introduce a change to github/gerrit handling code, e.g. the trigger mechanism - code that depends on Zuul or other Jenkins trigger plugins

1. Clone Jenkins job winci-server2016-prod to some temporary tmp-devel-gerrit-check
2. Configure tmp-devel-gerrit-check:
3. Properties content: BRANCH_NAME={branch to test}
4. Branches to build: {branch to test}
5. Schedule tmp-devel-gerrit-check job manually with parameters:
6. ZUUL_PROJECT=Juniper/contrail-controller
7. ZUUL_BRANCH=master
8. ZUUL_REF=None
9. ZUUL_URL=http://10.84.12.75/merge-warrior
10. ZUUL_UUID= (some random UUID - it will determine path on the logserver)
11. ZUUL_CHANGE= (can be left empty)
12. ZUUL_PATCHSET= (can be left empty)
13. Verify that it passes
14. (optional, recommended) Paste a link to successful build logs under your PR on github for the reviewers to verify
15. Remove temporary tmp-devel-gerrit-check job