RFR: 8240711: TestJstatdPort.java failed due to "ExportException: Port already in use:"

[Daniil Titov]

Please review the change [1] that fixes the intermittent failure of the test.

The problem here is that if the RMI port is in use than the test keep waiting for "jstatd started (bound to " to appear in the process output and in this case
It doesn't happen.

	at java.util.concurrent.CountDownLatch.await(java.base at 15-internal/CountDownLatch.java:232)
	at jdk.test.lib.process.ProcessTools.startProcess(ProcessTools.java:205)
	at jdk.test.lib.process.ProcessTools.startProcess(ProcessTools.java:133)
	at jdk.test.lib.process.ProcessTools.startProcess(ProcessTools.java:254)
	at jdk.test.lib.thread.ProcessThread$ProcessRunnable.xrun(ProcessThread.java:153)
	at jdk.test.lib.thread.XRun.run(XRun.java:40)
	at java.lang.Thread.run(java.base at 15-internal/Thread.java:832)
	at jdk.test.lib.thread.TestThread.run(TestThread.java:123)

Testing: Mach5 tests for sun/tools/jstatd/ successfully passed.  Tier1-tier3 tests are still in progress.

[1] http://cr.openjdk.java.net/~dtitov/8240711/webrev.01/
[2] https://bugs.openjdk.java.net/browse/JDK-8240711 


Thank you,
Daniil