misc/dashboard/builder: increase cmdTimeout to 10 minutes
misc/dashboard/builder: increase cmdTimeout to 10 minutes

It takes more then 5 minutes to clone go repo
on windows-386 builder now.

R=golang-dev, dave
CC=golang-dev
https://codereview.appspot.com/12007043

apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,pombredanne/go-deleteme,tv42/old-go,tv42/old-go,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,apparentlymart/golang,pombredanne/go-deleteme,apparentlymart/golang,tv42/old-go,tv42/old-go,tv42/old-go,apparentlymart/golang,apparentlymart/golang