RFR(XS): 8134583: sun.management.HotspotCompilation should handle absence of per-thread perf counters

[Claes Redestad]

Hi,

please review this patch to clean up and make 
sun.management.HotspotCompilation
behave nice if the VM would decide to no longer expose per-compiler 
thread perf counters:

webrev: http://cr.openjdk.java.net/~redestad/jdk9/8134583/webrev.00/
bug: https://bugs.openjdk.java.net/browse/JDK-8134583

/Claes