RFR 8249217: Unexpected StackOverflowError in "process reaper" thread still happens

[Roger Riggs]

Please review a change to the Process reaper thread initialization to 
preemptively
make sure classes ThreadLocalRandom and ConcurrentHashMap are initialized.
 From the stack overflow failures, it seems that the classes have not 
been initialized
before they are used during processing the termination of a process.
When the initialization is performed on the smaller reaper stack, it 
occasionally
exceeds the available stack.

As an aid to diagnostics, 
-XX:AbortVMOnException=java.lang.StackOverflowError
is added to TestHumongousNonArrayAllocation that has failed intermittently.
If the problem happens again it will produce an hs_error file with 
useful details
and will otherwise not change the test behavior.

Webrev:
    http://cr.openjdk.java.net/~rriggs/webrev-stackoverflow-8249217/

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8249217

Thanks, Roger