RFR: 8244340: Handshake processing thread lacks yielding

[Robbin Ehn]

Hi all, please review.

As the issue describes there are problems with this infinitely spinning.
To avoid any performance regression we do not yield while we do or see
progress. But when we enter a period of no progression we 'quickly' give
up.

Issue:
https://bugs.openjdk.java.net/browse/JDK-8244340

Code:
http://cr.openjdk.java.net/~rehn/8244340/v1/webrev/

In the pathologically case we can easily see 10x improvement starting 
the VM.
I have found no performance regressions or performance gains in our
standard benchmark setups.
But I see much better average completion times for handshakes.
For example specJVM2008 serial with ZGC shows 4x faster time to
completion for handshakes in my setup, but little or no effect on score
(ops/m).

Passes t1-3.

Thanks, Robbin