cmd/coordinator: fix nostream feature

Change-Id: Iae8c46ccf7d87ecd33850ed2c750cb81022be3eb
Reviewed-on: https://go-review.googlesource.com/10494
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

cmd/coordinator/coordinator.go

@@ -490,7 +490,7 @@ func handleLogs(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprintf(w, "\n\n(no live streaming. reload manually to see status)\n")
 		st.mu.Lock()
 		defer st.mu.Unlock()
-		st.output.WriteTo(w)
+		w.Write(st.output.Bytes())
 		return
 	}