Somehow nodenum was getting reset to zero (and saved to flash - which is
bad because it makes the failure permanent). So I've changed nodenum
selection to occur after we load the saved preferences (and we try to keep
nodenum stable in that case).
I'm puzzled as to how it ever got set to zero (unless there *shudder*
is some errant pointer that clobbered it). But next week I'm turning
4 byte nodenums back on, which will make this moot - because they
will always be based on macaddr and the current process where nodes
haggle with the mesh to pick a unique one-byte nodenum will be gone.
