Add RHEL6-specific upstart config files

RHEL6 doesn't use the net-device-up and local-filesystems targets,
meaning that if someone decides to use this upstart config then the
master/minion/syndic does not start on boot.

We don't deploy upstart configs in our RPMs, but this provides a working
upstart config file for those that wish to use it.
Merge pull request #10785 from terminalmage/rhel6-upstart

Add RHEL6-specific upstart config files