RFR 8145982: JMXInterfaceBindingTest is failing intermittently

[Jaroslav Bachorik]

Please, review this trivial test change

Issue : https://bugs.openjdk.java.net/browse/JDK-8145982
Webrev: http://cr.openjdk.java.net/~jbachorik/8145982/webrev.00

The test calls System.exit(0) in case when it is not applicable (due to 
HW configuration). This call is forbidden by the test harness and the 
test fails. The solution is to replace it with 'return'.

Thanks!

-JB-