RFR 8049194: com/sun/tools/attach/StartManagementAgent.java start failing after JDK-8048193

[Jaroslav Bachorik]

Please, review the following test change

Issue : https://bugs.openjdk.java.net/browse/JDK-8049194
Webrev: http://cr.openjdk.java.net/~jbachorik/8049194/webrev.00

jdk.testlibrary.ProcessThread was erroneously starting the external 
application with timeout of -1 - meaning no waiting for the target 
application to initialize. What it should have done was to wait for the 
target application indefinitely and let the harness timeout the test.

The change modifies jdk.testlibrary.ProcessTools.startProcess() methods 
to be explicit about the meaning of "-1" and "0" (newly added) timeouts. 
It also adds a convenient method where you can start a process waiting 
for the warmup indefinitely without actually providing "0" and a dummy 
TimeUnit.

I also took liberty and encapsulated the "test.timeout.factor" system 
property handling into jdk.testlibrary.Utils.adjustTimeou(to) method.

The changes to the test library keep the current semantics (eg. the 
timeout of -1 still means no wait etc.) - they are only enhancing it.

Thanks,

-JB-