RFR 8061312: Even more debug output needed

[Jaroslav Bachorik]

Please, review the following addition to the test debug output
Issue      : https://bugs.openjdk.java.net/browse/JDK-8061312
Test Issue : https://bugs.openjdk.java.net/browse/JDK-8059949
Webrev     : http://cr.openjdk.java.net/~jbachorik/8061312/webrev.00

The test 'com/sun/tools/attach/StartManagementAgent.java' is failing 
intermittently with timeouts. This change is to add more debug output to 
enable locating where the test gets stuck.

Thanks,

-JB-