[Testbug] serviceability/sa/Jhsdb* tests can't tolerate unrelated warnings

Test: serviceability/sa/JhsdbThreadInfoTest.java

 stderr: [Java HotSpot(TM) 64-Bit Server VM warning: Global variable for obsolete special flag entry "UseMembar" should be removed
Java HotSpot(TM) 64-Bit Server VM warning: Global variable for obsolete special flag entry "FastTLABRefill" should be removed
Java HotSpot(TM) 64-Bit Server VM warning: Global variable for obsolete special flag entry "SafepointSpinBeforeYield" should be removed
Java HotSpot(TM) 64-Bit Server VM warning: Global variable for obsolete special flag entry "DeferThrSuspendLoopCount" should be removed
Java HotSpot(TM) 64-Bit Server VM warning: Global variable for obsolete special flag entry "DeferPollingPageLoopCount" should be removed
Java HotSpot(TM) 64-Bit Server VM warning: Global variable for expired flag entry "UseCGroupMemoryLimitForHeap" should be removed
]
 exitValue = 0

java.lang.Error: Couldn't start jhsdb, attach to LingeredApp or match ThreadName: java.lang.RuntimeException: stderr was not empty
at JhsdbThreadInfoTest.main(JhsdbThreadInfoTest.java:78)

Similarly for serviceability/sa/TestJhsdbJstackLock.java

The tests contain:

    out.stderrShouldBeEmpty();

to watch for unexpected problems, but that also catches unrelated VM warnings.