RFR JDK-8195703: BasicJDWPConnectionTest.java: 'App exited unexpectedly with 2'

[Alex Menkov]

Hi all,

please review a fix for
https://bugs.openjdk.java.net/browse/JDK-8195703
webrev:
http://cr.openjdk.java.net/~amenkov/BasicJDWPConn/webrev.01/

I was not able to reproduce the issue, but accordingly the logs in jira 
root cause is a transport initialization error "Address already in use".
The test uses Utils.getFreePort() to select some free port, but it can 
be race condition when some other app (or other test) uses the port 
selected before debuggee application starts to listen on it.
The fix uses dynamic port allocation and then parses it from the 
debuggee output.
Other changes:
- dropped catching exceptions and calling System.exit() - this causes 
SecurityException in JTReg harness which makes error analysis much harder;
- dropped using of Utils.getFreePort() from jdi/DoubleAgentTest.java test;
   jdi/BadHandshakeTest.java also uses Utils.getFreePort(), but it 
handles "Already in use" error re-peeking other free port and restarting 
debuggee, so I keep it as is.

--alex