test: make goprint.go wait longer for go its routine to execute
test: make goprint.go wait longer for go its routine to execute

Update issue 5281

R=golang-dev, r, bradfitz, cshapiro
CC=golang-dev
https://codereview.appspot.com/8631047

h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang,h8liu/golang