common.sh: Changed "route" for "/sbin/route"

In some computers (e.g. UCA Classmates), route path is not defined in the
PATH variable.

Signed-off-by: Erik Alexandre Pucci <eap08@c3sl.ufpr.br>
Acked-by: Diego Giovane Pasqualin <dgp06@c3sl.ufpr.br>
Signed-off-by: Danilo K. S. Yorinori <danilok@c3sl.ufpr.br>