test: attempt at making a test more robust
test: attempt at making a test more robust

A current theory is that this test is too fast for the
time resolution on the VMs where our builders run.

R=rsc
CC=golang-dev
http://codereview.appspot.com/5581056

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