8253752: jdk/test/sun/management/jmxremote/bootstrap/RmiBootstrapTest.sh fails randomly

[hedongbo]

Hi,

Please review this 8u test-only changes.

Bug: https://bugs.openjdk.java.net/browse/JDK-8253752
webrev: http://cr.openjdk.java.net/~dongbohe/8253752/webrev.00/

Testing:  Worked correctly after patch.

Thanks,
dongbohe