RFR [13] 8170705: sun/net/www/protocol/http/StackTraceTest.java fails intermittently with Invalid Http response

[Chris Hegarty]

This review is for a test only change. It resolves a rare intermittent
failure.

The issue is that the test creates, retrieves the local port, and
immediately closes a server socket. It then expects this port to refuse
subsequent connections. This is an anti-pattern, since on a busy machine
the port may be reused ( and subsequently accept future connections ),
before this test attempts to connect.

The solution is to use the test library `Utils::refusingEndpoint` to
retrieve a local address that will refuse connections.

http://cr.openjdk.java.net/~chegar/8170705/

-Chris.