fixed various issues with testnode and make it even more robust

Here the list of changes:
- close all timers when quitting, this makes stopping an erp5tetsnode
  much faster
- remove hack on slapos/testnode after fix of slapos.cookbook
- remove old tmp files left by buildout (buildout has te bo fixed too)
- remove logging handlers where the are not needed any more
- fixed the kill command, it was not able to kill properly childs
release erp5.util 0.4.25
make sure to not make erp5testnode failing if temp folder was already removed