RFR 6791551: ExclusiveBind.java has a race condition

[Jaroslav Bachorik]

Please, review the following test fix:

Issue : https://bugs.openjdk.java.net/browse/JDK-6791551
Webrev: http://cr.openjdk.java.net/~jbachorik/6791551/webrev.00

The fix prevents the situation when the first debuggee has not managed 
to finish its intialization while the second one is started up thus 
making the port available for the second debuggee and failing the test.

The patch is using the library methods to configure and launch the 
debuggee and the test waits for the well known string to appear in the 
first debuggee output before attempting to launch the second debuggee.

Thanks,

-JB-