JCL_Test test_suspend IllegalThreadStateException: Has threads

[pshipton]

https://openj9-jenkins.osuosl.org/job/Test_openjdk11_j9_sanity.functional_s390x_linux_Nightly_testList_1/412 JCL_Test_0

FAILED: test_suspend
java.lang.IllegalThreadStateException: Has threads
	at java.base/java.lang.ThreadGroup.destroyImpl(ThreadGroup.java:270) from jrt:/java.base
	at java.base/java.lang.ThreadGroup.destroy(ThreadGroup.java:252) from jrt:/java.base
	at java.base/java.lang.ThreadGroup.destroyImpl(ThreadGroup.java:277) from jrt:/java.base
	at java.base/java.lang.ThreadGroup.destroy(ThreadGroup.java:252) from jrt:/java.base
	at org.openj9.test.java.lang.Test_ThreadGroup.test_suspend(Test_ThreadGroup.java:752) from jdk.internal.loader.ClassLoaders$AppClassLoader@bc936c00(file:/home/jenkins/workspace/Test_openjdk11_j9_sanity.functional_s390x_linux_Nightly_testList_1/jvmtest/functional/Java8andUp/GeneralTest.jar)