runtime: add missing if(raceenabled)
runtime: add missing if(raceenabled)

R=0xe2.0x9a.0x9b, minux.ma, iant, dave
CC=golang-dev
http://codereview.appspot.com/6654052

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