[TESTBUG] JFR TestShutdownEvent fails on some systems due to process surviving SIGINT

This issue was reported by Goetz; it is specific to some SAP systems. I was unable to reproduce it in Oracle test system so far.

Test case (sub-test) that fails: TestSig
    Log states: "Running subtest 7 (jdk.jfr.event.runtime.TestShutdownEvent$TestSig)"

Error message:
=========================
Exception in thread "main" java.lang.RuntimeException: Process survived the SIGINT signal!
at jdk.test.lib.Asserts.fail(Asserts.java:594)
at jdk.jfr.event.runtime.TestShutdownEvent$TestSig.runTest(TestShutdownEvent.java:230)
at jdk.jfr.event.runtime.TestShutdownEvent$TestMain.main(TestShutdownEvent.java:111)

Exit code: 1
Error: Value not equal to Shutdown requested from Java, field='reason', value='No remaining non-daemon Java threads': expected No remaining non-daemon Java threads to equal Shutdown requested from Java
=========================

Proposed solution:
   Instead of asserting when the process survived SIGINT (or other signal), the test case should be more flexible/robust and skip the rest of the test case, continue to the rest of the test.