If on redraw() we find z has changed, refetch the nodes from the database
If on redraw() we find z has changed, refetch the nodes from the database

This finally fixes (I hope) the "go to active node" shortcut.

htem/CATMAID,htem/CATMAID,fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID,fzadow/CATMAID,fzadow/CATMAID,htem/CATMAID