Relax 053-wait-some sucess criteria

Drop constraint on total extra delay. Shorten maximum wait time.

But then only only require success in 2 out of 3 runs.

Switch timing to use nanoTime() to get a monotonic clock. This might
have contributed to a few of the observed failures.

Bug: 175435088

Test: Prun-test --host 053-wait-some
Test: Retest with sleepy.wait(delay * 3/2); on line 66.
Test: Retest with timing set to true in code.
Change-Id: Ic8e392340ba1d70782f2a5303bfebf1d7251a86b