jenkins: add in ganglia monitoring

Ganglia has a plugin to monitor Jenkins job queues. Might want to have
it on the Jenkins master.

Source:
https://github.com/ganglia/gmond_python_modules

I have edited the .pyconf to points to http://127.0.0.1:8080/ci and
tested the entry point on gallium using curl:

 $ curl 'http://127.0.0.1:8080/ci/api/json'
 // bunch of json

bug: 47884
Change-Id: Ie347ec6ef23224b01740f03ea6360fcc3b3f0ccd