jenkins: fix up ganglia monitoring

The Ganglia plugin 'jenkins' is imported by gmond using the system path
before the configured module path. Since we have python-jenkins
installed, gmond will attempt to load that instead of the actual Ganglia
plugin.

I have renamed the plugin to gmond_jenkins to avoid the conflict though
the files keep the same name in puppet to ease future updates / diffs.

Change-Id: Idad0a207e85586c476ed16955ecfeb5401f6bbf3
Merge "jenkins: fix up ganglia monitoring" into production