make log watching more amenable to resource cleanup (#515)
make log watching more amenable to resource cleanup (#515)

* make log watching more amenable to resource cleanup

* add timeout to event wait

* better docstring

* prevent log scan race condition

each scan records the max extent of the log file, then does a scan which
will cover the file to that point, then records that point, which can
then be used in the next iteration as the log start point.

* deduplicate

* use proper logging

* better docstring

mike-tr-adamson/ccm,mikefero/ccm,pcmanus/ccm,tolbertam/ccm,thobbs/ccm,tolbertam/ccm,pcmanus/ccm,bcantoni/ccm,mike-tr-adamson/ccm,bcantoni/ccm,thobbs/ccm,mikefero/ccm,pcmanus/ccm,mike-tr-adamson/ccm