Quickfix for logplex refc binary leak

This fix is temporary. It garbage collects the node once it
reaches too high of a memory threshold in an attempt to protect
against failure due to OOMs following refc binaries leak.
Merge pull request #48 from heroku/refc-leak-quickfix

Quickfix for logplex refc binary leak
Merge branch 'v69' into v69-R16B01