RFR 8077953: [TEST_BUG] com/sun/management/OperatingSystemMXBean/TestTotalSwap.java Compilation failed after JDK-8077387

[Jaroslav Bachorik]

Please, review this JDK8 only test change

Issue : https://bugs.openjdk.java.net/browse/JDK-8077953
Webrev: http://cr.openjdk.java.net/~jbachorik/8077953/webrev.00
Backport of https://bugs.openjdk.java.net/browse/JDK-8077387 requires 
testlibrary functionality not yet backported to JDK8. This patch takes 
care of bringing that functionality there.

Thanks,

-JB-