Bug 1121217 - Symbol leak in Throttler cgroup code

* Enhance debugging output
* Remove to_sym in keys
Bug 1121217 - Symbol leak in Throttler cgroup code

* fix tests
Merge pull request #5697 from jwhonce/stage

Merged by openshift-bot
Automatic commit of package [rubygem-openshift-origin-node] release [1.28.6-1].
Automatic commit of package [openshift-origin-node-util] release [1.27.6-1].