RFR(S): JDK-8029808 com/sun/jdi/ProcessAttachTest.sh times out

[Staffan Larsen]

webrev: http://cr.openjdk.java.net/~sla/8029808/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8029808

I have tried to improve the stability of this test in a couple of ways.

- Timeout set to 120s - it should never need to run that long
- When we start the debugee, we wait for the port-file to become available instead of waiting for output from the process. This should be less racy.
- stderr output from the debuggee and ShutdownDebuggee programs are captured with the stdout output
- Moved “sleep 1” to after the check for the port file so the test is faster if the file already exists

I’m not sure any of these are the cause of the timeout, but at least it should be a bit more stable now.

/Staffan