8081775: two lib/testlibrary tests are failing with "Error. failed to clean up files after test" with jtreg 4.1 b12
Reviewed-by: sla
Contributed-by: amy.lu@oracle.com

8081347: Add @modules to jdk_core tests
Reviewed-by: alanb, joehw, lancea
Contributed-by: alexander.kulyakhtin@oracle.com, alan.bateman@oracle.com, mandy.chung@oracle.com

8066106: sun/tools/jps/TestJpsClass.java failed to remove stale attach pid file
Reviewed-by: jbachorik

8056143: interrupted java/lang/management/MemoryMXBean/LowMemoryTest.java leaves running process
Reviewed-by: sla, dholmes

8007142: Add utility classes for writing better multiprocess tests in jtreg
Reviewed-by: alanb, rbackman