RFR (XS): 8214208: Nestmate package validation logging/exception should include classloader information

[David Holmes]

bug: https://bugs.openjdk.java.net/browse/JDK-8214208
webrev: http://cr.openjdk.java.net/~dholmes/8214208/webrev/

This is a simple change to add classloader information to the logging 
and exceptions related to obtaining the nest-host within the VM.

This makes it simpler to see when tests fail due to nested types being 
loaded by different classloaders.

Of course the test had to be updated to account for the additional 
information.

Testing: runtime/Nestmates
          tier 1 - 2

Thanks,
David