RFR(S): 8220672: [TESTBUG] TestCPUSets should check that cpuset does not exceed available cores

[mikhailo.seledtsov at oracle.com]

Please review this change that fixes the TestCPUSets test. In short, in 
some configurations the size of CPU set
exceeds the available amount of cores; see bug description and comments 
for details.
The fix (or some may say work-around) in this change is to limit the 
size of the set to the number of available CPUs.

     JBS: https://bugs.openjdk.java.net/browse/JDK-8220672
     Webrev: http://cr.openjdk.java.net/~mseledtsov/8220672.00/
     Testing:
       - ran the affected test on hosts where issue occurred
       - ran the affected test on a variety of hosts in build-and-test 
cluster
       The problem does not show up anymore.

Thank you,
Misha