prevent op/time.t failures on NetBSD 5.1

prevent op/time.t failures on NetBSD 5.1

- make the watchdog time exceed the maximum time for the "very basic times
  test".  This doesn't prevent the test from failing, but prevents the
  entire test script from being killed by the watchdog if the times()
  test does fail

- do more work inside the loop, with the previous "burn cycles" loop
  system time was increasing but user time stayed at its starting value.