RFR(S): 7145419 com/sun/jdi/JdbMethodExitTest.sh fails when a background thread is generating events.

[Staffan Larsen]

This test fails if there are background threads that run while the test is running. I've modified the test to use the "trace" commands in jdb with the extra thread parameter. I have assumed that the main thread has thread id 1. "trace" with thread id behaves a little bit different so a couple of extra "cont" were needed.

webrev: http://cr.openjdk.java.net/~sla/7145419/webrev.00/

Thanks,
/Staffan