Protect against divide-by-0 when BW of a link is '*' (which appears as 0 in ltmap).
Protect against divide-by-0 when BW of a link is '*' (which appears as 0 in ltmap).

The better fix would be to have the generator of ltmap fill in the "native" BW
of the physical link in question.

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