Bug 1086104 - improve the setting of TC_CHECK in oo-accept-node

By default TC is enabled.  Previously this check was assuming false if
TRAFFIC_CONTROL_ENABLED wasn't set.
Improving the inline docs for TRAFFIC_CONTROL_ENABLED in node.conf
Merge pull request #5269 from brenton/BZ1086104

Merged by openshift-bot
Bug 1087755 - node.conf#TRAFFIC_CONTROL_ENABLED defaults to true

* Fix check to assume true not false