[11u] RFR: 8238270: java.net HTTP/2 client does not decrease stream count when receives 204 response

[Lindenmaier, Goetz]

Hi,

I am downporting this for parity with 11.0.9-oracle.
I had to resolve the copyright in Stream.java
And I had to adapt the test as testlibrary file SimpleSSLContext
Is at a different location.  All trivial adaptions.

http://cr.openjdk.java.net/~goetz/wr20/8238270-Http2_204-jdk11/01/

Please review.

https://bugs.openjdk.java.net/browse/JDK-8238270
https://hg.openjdk.java.net/jdk/jdk/rev/fd72cd98180e

Best regards,
  Goetz