RFR(S): 8217744: [TESTBUG] JFR TestShutdownEvent fails on some systems due to process surviving SIGINT

[mikhailo.seledtsov at oracle.com]

Please review: this change updated the handling of cases where child 
process survives the signal. If it does,
we record this and skip verification, and continue with the rest of the 
test.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8217744
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8217744.00/
     Testing:
         1. Locally: Mac OSX, both as is and simulating the child 
process surviving the SIGINT - PASS
         2. Multi-platform automated system: Linux-x64, Win-x64, Mac, 
Sol-Spc - All PASS
         3. SAP engineer tested the patch on the SAP systems where it 
originally failed - Pass
             Goetz, many thanks for testing the patch.

Thank you,
Misha