SH-4090 Integrating deadman timer with mesh repo downloads.

Timer interface violated my design rules and I paid for it
with clumsiness and silent errors.  Cleaned it up mainly
removing the evil default values.  Found better integration
points in the mesh downloader and it's producing fairly
consistent numbers on the MeshTest2 test region (about
5500 downloads, ~90 seconds, +/- 10 seconds).  Will review
with davep and do an early timer stop on teleport which
invalidates a timing sequence.