RFR: 8291226: Create Test Cases to cover scenarios for JDK-8278067

[Ramesh Bhagavatam Gangadhar]

There are total 160 scenarios written with combination of client properties (Client Scenarios) and Server Response (Server Scenarios).
In tabular format, Client and Server scenarios along with expected output are documented here:[Permalink](https://bugs.openjdk.org/browse/JDK-8291226?focusedCommentId=14519074&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14519074)
This Program Should be run mandatorily in othervm mode itself since it has system property changes so can't be clubbed with other scenarios. so each scenario should be run in individual JVM.
For each and every scenario, ServerSocket is created and waits for clients to connect to it.
isProxySet and serverReady are shared variables between server thread and client thread(main) and it should be set and reset to false for each and every scenario.
isProxySet and serverReady variables should be set by server thread before proceeding to client thread(main).
if isProxySet variable is set to true then client set the proxy value to url.openConnection(Proxy)
if (isProxySet) { httpUrlConnection = (sun.net.www.protocol.http.HttpURLConnection) url .openConnection(new Proxy(Type.HTTP, new InetSocketAddress("localhost", SERVER_PORT))); } else { httpUrlConnection = (sun.net.www.protocol.http.HttpURLConnection) url.openConnection(); }
Program tries to fetch the Value of <Key, Value> Pairs of HashMap KeepAliveCache where Key is KeepAliveKey and Value is ClientVector KeepAliveTimeout is stored in Value ClientVector of HashMap KeepAliveCache.
if connection is cached then KeepAliveTimeout is stored in ClientVector. KeepAliveTimeout stored in Value(ClientVector) of HashMap KeepAliveCache is compared with Expected Value.
if connection is not cached then connection is terminated immediately.

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Commit messages:
 - Create KeepAliveTest

Changes: https://git.openjdk.org/jdk/pull/9958/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=9958&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8291226
  Stats: 586 lines in 1 file changed: 586 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/9958.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9958/head:pull/9958

PR: https://git.openjdk.org/jdk/pull/9958