Improve upstream gjjb jobs, add Github version

ODL already has the upstream LF Gerrit in its Gerrit triggers, and it
is named "lf-releng". This should therefore be used as the standard
name for other projects.

Added a Github version of the upstream global-jjb verify, which just
needs SCM changes for pulling in its ci-man repo.

Documentation for preparing a Jenkins server to test upstream gjjb
changes is available here: https://confluence.linuxfoundation.org/display/RELEN/Add+upstream+global-jjb+testing+to+Jenkins

Issue: RELENG-1043
Change-Id: I0a2f757c0e58355bc59eaa1e56eaa396f60b0f32
Signed-off-by: Eric Ball <eball@linuxfoundation.org>