Prevent getRoot() from going into an infinite loop.
Prevent getRoot() from going into an infinite loop.

This is almost certainly not the right fix, but I don't grok the code
(at least in part because the calculated %linparents hash is never used!)

nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome,nmc-probe/emulab-nome