7012823: TEST_BUG: java/nio/MappedByteBuffer tests leave file mappings that prevent clean-up (win)

[Alan Bateman]

Two of the MappedByteBuffer tests fail intermittently on Windows when 
running jtreg with -retain:fail,error. The tests don't actually fail but 
rather it's that jtreg can't remove the files that the tests leave 
behind.  To avoid these failure I'd like to change these tests so that 
they use files in the temporary file directory and in addition, do a 
GC+sleep at the end to improve the change that the files will be 
unmapped before the VM terminates. The webrev with the changes is here:
  http://cr.openjdk.java.net/~alanb/7012823/webrev/

Thanks,
Alan.