JDK 9 RFR of 8175033: (se) Improve internal timing of java/nio/channels/Selector/WakeupAfterClose.java

[Brian Burkhalter]

Please review at your convenience.

Issue:	https://bugs.openjdk.java.net/browse/JDK-8175033
Patch:	http://cr.openjdk.java.net/~bpb/8175033/webrev.00/

Improve the probability that the spawned thread will be blocked in select() before the main thread calls close() on the Selector thus hopefully averting the recurrence of [1].

Thanks,

Brian

[1] https://bugs.openjdk.java.net/browse/JDK-8143614